<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:895c872f-3428-4d0e-80ef-7e94d5cf51bb,g:86a6affd-b4cf-4d76-b240-eb1a79a28e64-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.fiserv.com/role/CoverPage" xlink:type="simple" xlink:href="fi-20251231.xsd#CoverPage"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/CoverPage" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_c4ab1d89-d6de-4fbc-a4e4-ca2a9308632c" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_DocumentInformationTable_c4ab1d89-d6de-4fbc-a4e4-ca2a9308632c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_9b471180-f63c-430c-95df-bea9b86755fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_c4ab1d89-d6de-4fbc-a4e4-ca2a9308632c" xlink:to="loc_us-gaap_StatementClassOfStockAxis_9b471180-f63c-430c-95df-bea9b86755fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_9b471180-f63c-430c-95df-bea9b86755fa_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_9b471180-f63c-430c-95df-bea9b86755fa" xlink:to="loc_us-gaap_ClassOfStockDomain_9b471180-f63c-430c-95df-bea9b86755fa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_cee1802c-b67c-4935-9c7e-cf9da4bcf031" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_9b471180-f63c-430c-95df-bea9b86755fa" xlink:to="loc_us-gaap_ClassOfStockDomain_cee1802c-b67c-4935-9c7e-cf9da4bcf031" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_53fade85-6aa3-45cd-b8ba-73157a628868" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_cee1802c-b67c-4935-9c7e-cf9da4bcf031" xlink:to="loc_us-gaap_CommonStockMember_53fade85-6aa3-45cd-b8ba-73157a628868" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A1.125SeniorNotesDueJuly2027Member_45bcbb90-b818-4184-935a-a1de00d5a685" xlink:href="fi-20251231.xsd#fi_A1.125SeniorNotesDueJuly2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_cee1802c-b67c-4935-9c7e-cf9da4bcf031" xlink:to="loc_fi_A1.125SeniorNotesDueJuly2027Member_45bcbb90-b818-4184-935a-a1de00d5a685" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A1.625SeniorNotesDue2030Member_dcd6aa3b-0a5a-4679-a998-0e48978366e1" xlink:href="fi-20251231.xsd#fi_A1.625SeniorNotesDue2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_cee1802c-b67c-4935-9c7e-cf9da4bcf031" xlink:to="loc_fi_A1.625SeniorNotesDue2030Member_dcd6aa3b-0a5a-4679-a998-0e48978366e1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A3000SeniorNotesDue2031Member_28fb530d-4d9f-47be-a427-562f1c837b67" xlink:href="fi-20251231.xsd#fi_A3000SeniorNotesDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_cee1802c-b67c-4935-9c7e-cf9da4bcf031" xlink:to="loc_fi_A3000SeniorNotesDue2031Member_28fb530d-4d9f-47be-a427-562f1c837b67" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A4500SeniorNotesDue2031Member_6fdbe871-c630-466c-9843-379089f68cee" xlink:href="fi-20251231.xsd#fi_A4500SeniorNotesDue2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_cee1802c-b67c-4935-9c7e-cf9da4bcf031" xlink:to="loc_fi_A4500SeniorNotesDue2031Member_6fdbe871-c630-466c-9843-379089f68cee" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A2.875SeniorNotesDue2028Member_a7aa0e83-2c95-4c52-b54d-05cb5086dbc4" xlink:href="fi-20251231.xsd#fi_A2.875SeniorNotesDue2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_cee1802c-b67c-4935-9c7e-cf9da4bcf031" xlink:to="loc_fi_A2.875SeniorNotesDue2028Member_a7aa0e83-2c95-4c52-b54d-05cb5086dbc4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A3.500SeniorNotesDue2032Member_2d431d5c-4542-4933-9dc7-b6facc79860e" xlink:href="fi-20251231.xsd#fi_A3.500SeniorNotesDue2032Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_cee1802c-b67c-4935-9c7e-cf9da4bcf031" xlink:to="loc_fi_A3.500SeniorNotesDue2032Member_2d431d5c-4542-4933-9dc7-b6facc79860e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A4.000SeniorNotesDue2036Member_a45915bd-c4d8-467f-9fc9-510ff565891c" xlink:href="fi-20251231.xsd#fi_A4.000SeniorNotesDue2036Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_cee1802c-b67c-4935-9c7e-cf9da4bcf031" xlink:to="loc_fi_A4.000SeniorNotesDue2036Member_a45915bd-c4d8-467f-9fc9-510ff565891c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_b5294417-1a73-41a8-90bb-9c76d2d81dd7" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_DocumentType_b5294417-1a73-41a8-90bb-9c76d2d81dd7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentAnnualReport_09a75376-d740-4f3a-88e5-1f0acdfbaee9" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentAnnualReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_DocumentAnnualReport_09a75376-d740-4f3a-88e5-1f0acdfbaee9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_8df465b7-2e07-4f60-b1c1-e2e66799fb32" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_DocumentPeriodEndDate_8df465b7-2e07-4f60-b1c1-e2e66799fb32" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_beafdbac-398a-44ea-835f-28d09b56ac8f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_CurrentFiscalYearEndDate_beafdbac-398a-44ea-835f-28d09b56ac8f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_caf2813b-ea2a-4079-a45e-63f2daa56c1b" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_DocumentTransitionReport_caf2813b-ea2a-4079-a45e-63f2daa56c1b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_5a8ecbb5-cbec-4b38-aa4e-41192eb26c33" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityFileNumber_5a8ecbb5-cbec-4b38-aa4e-41192eb26c33" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_86318b34-ee0a-4e02-b0b3-9a3cb5ebf3e5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityRegistrantName_86318b34-ee0a-4e02-b0b3-9a3cb5ebf3e5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_214f38e1-d7b6-429a-a50e-693c1381cf91" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityIncorporationStateCountryCode_214f38e1-d7b6-429a-a50e-693c1381cf91" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_59557c51-60a5-49d3-bc60-88e3c2189216" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityTaxIdentificationNumber_59557c51-60a5-49d3-bc60-88e3c2189216" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_6ee3bd07-2979-4656-9a5f-a32f4d9c522f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityAddressAddressLine1_6ee3bd07-2979-4656-9a5f-a32f4d9c522f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_44a3e697-623a-4473-b3bc-d812970019b5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityAddressCityOrTown_44a3e697-623a-4473-b3bc-d812970019b5" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_476544cd-f5b7-49b2-91ca-c10ba6a7d3f5" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityAddressStateOrProvince_476544cd-f5b7-49b2-91ca-c10ba6a7d3f5" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_1dbe29e7-395d-4633-bb79-4e3e7faaaefa" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityAddressPostalZipCode_1dbe29e7-395d-4633-bb79-4e3e7faaaefa" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_8e3cc4d1-0797-4016-999c-0e4a189b770f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_CityAreaCode_8e3cc4d1-0797-4016-999c-0e4a189b770f" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_1352eaf4-2d8c-4e9c-83a6-5bef406e8519" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_LocalPhoneNumber_1352eaf4-2d8c-4e9c-83a6-5bef406e8519" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_d8a5a6a0-34ad-45ee-bbc1-de02c84e9aee" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_Security12bTitle_d8a5a6a0-34ad-45ee-bbc1-de02c84e9aee" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_22b1320b-6fb8-4bcc-9c78-c8bba46da594" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_TradingSymbol_22b1320b-6fb8-4bcc-9c78-c8bba46da594" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_a0a30e9b-70d8-45a1-af9c-20647705f999" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_SecurityExchangeName_a0a30e9b-70d8-45a1-af9c-20647705f999" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityWellKnownSeasonedIssuer_32efda89-2444-478a-b558-498834688424" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityWellKnownSeasonedIssuer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityWellKnownSeasonedIssuer_32efda89-2444-478a-b558-498834688424" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityVoluntaryFilers_26df7671-a8ad-4806-a1a8-96b5ddb50841" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityVoluntaryFilers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityVoluntaryFilers_26df7671-a8ad-4806-a1a8-96b5ddb50841" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_1641f2e4-0246-4816-97b1-c941fa20ded0" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityCurrentReportingStatus_1641f2e4-0246-4816-97b1-c941fa20ded0" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_6372e80f-fbf8-4a7c-adcc-4546d7d5bae9" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityInteractiveDataCurrent_6372e80f-fbf8-4a7c-adcc-4546d7d5bae9" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_927fb56d-d7e9-4dbe-bd17-59b6d2f10bda" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityFilerCategory_927fb56d-d7e9-4dbe-bd17-59b6d2f10bda" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_491e5c23-fef4-4827-b552-835fa3d86435" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntitySmallBusiness_491e5c23-fef4-4827-b552-835fa3d86435" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_1ffbfab0-636b-4909-836b-23eb7ce1e087" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityEmergingGrowthCompany_1ffbfab0-636b-4909-836b-23eb7ce1e087" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_IcfrAuditorAttestationFlag_49fa81b2-d60d-4e47-8672-2d93c9def20c" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_IcfrAuditorAttestationFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_IcfrAuditorAttestationFlag_49fa81b2-d60d-4e47-8672-2d93c9def20c" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFinStmtErrorCorrectionFlag_d3ce4f75-6a2c-4407-afa4-f39121b60ae9" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentFinStmtErrorCorrectionFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_DocumentFinStmtErrorCorrectionFlag_d3ce4f75-6a2c-4407-afa4-f39121b60ae9" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_3d1c93a1-bd74-419f-8132-8c17e952635d" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityShellCompany_3d1c93a1-bd74-419f-8132-8c17e952635d" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityPublicFloat_37cbb0a1-36e3-4ec1-be52-805fede43d36" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityPublicFloat"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityPublicFloat_37cbb0a1-36e3-4ec1-be52-805fede43d36" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_75e12bbb-709e-469a-b93f-20de8380b9ae" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_75e12bbb-709e-469a-b93f-20de8380b9ae" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentsIncorporatedByReferenceTextBlock_5f89e166-d84a-4c35-9dd9-8739ced096a7" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentsIncorporatedByReferenceTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_DocumentsIncorporatedByReferenceTextBlock_5f89e166-d84a-4c35-9dd9-8739ced096a7" xlink:type="arc" order="30"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_17fe03ea-6c1a-462c-87de-4f618f2f991b" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_EntityCentralIndexKey_17fe03ea-6c1a-462c-87de-4f618f2f991b" xlink:type="arc" order="31"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_3bec6ac2-47fe-471a-b291-9ef9369d5813" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_DocumentFiscalYearFocus_3bec6ac2-47fe-471a-b291-9ef9369d5813" xlink:type="arc" order="32"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_075c8649-57aa-4832-b43b-d614b3df12f9" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_DocumentFiscalPeriodFocus_075c8649-57aa-4832-b43b-d614b3df12f9" xlink:type="arc" order="33"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_54c3e3d3-1380-403c-8352-1b9bda785726" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_f3374831-1aec-4629-ac41-2272951f4d1f" xlink:to="loc_dei_AmendmentFlag_54c3e3d3-1380-403c-8352-1b9bda785726" xlink:type="arc" order="34"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/ConsolidatedStatementsofIncome" xlink:type="simple" xlink:href="fi-20251231.xsd#ConsolidatedStatementsofIncome"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/ConsolidatedStatementsofIncome" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_76adeff1-2c11-4ac6-bbc7-2bcacf236172" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:to="loc_us-gaap_StatementTable_76adeff1-2c11-4ac6-bbc7-2bcacf236172" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_cc1235cf-0e77-4bff-ba6e-a82ba4c5b36d" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_76adeff1-2c11-4ac6-bbc7-2bcacf236172" xlink:to="loc_srt_ProductOrServiceAxis_cc1235cf-0e77-4bff-ba6e-a82ba4c5b36d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_cc1235cf-0e77-4bff-ba6e-a82ba4c5b36d_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_cc1235cf-0e77-4bff-ba6e-a82ba4c5b36d" xlink:to="loc_srt_ProductsAndServicesDomain_cc1235cf-0e77-4bff-ba6e-a82ba4c5b36d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_4ef3785f-0ba9-4c70-aa00-9c081feaa7f4" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_cc1235cf-0e77-4bff-ba6e-a82ba4c5b36d" xlink:to="loc_srt_ProductsAndServicesDomain_4ef3785f-0ba9-4c70-aa00-9c081feaa7f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_ProcessingAndServicesMember_189e3d1f-76b0-46e3-988c-2ca272e06125" xlink:href="fi-20251231.xsd#fi_ProcessingAndServicesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_4ef3785f-0ba9-4c70-aa00-9c081feaa7f4" xlink:to="loc_fi_ProcessingAndServicesMember_189e3d1f-76b0-46e3-988c-2ca272e06125" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductMember_4a700e2a-8beb-41d5-ab92-79d4e3650fd9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_4ef3785f-0ba9-4c70-aa00-9c081feaa7f4" xlink:to="loc_us-gaap_ProductMember_4a700e2a-8beb-41d5-ab92-79d4e3650fd9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_200d169a-17f0-4729-a5b7-f1d78d9bc2d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:to="loc_us-gaap_RevenuesAbstract_200d169a-17f0-4729-a5b7-f1d78d9bc2d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_6acc1bfe-d9fe-4713-a81e-5db71346ff5f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_200d169a-17f0-4729-a5b7-f1d78d9bc2d1" xlink:to="loc_us-gaap_Revenues_6acc1bfe-d9fe-4713-a81e-5db71346ff5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_05c032eb-40a3-4854-8399-ce3523c6f022" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_05c032eb-40a3-4854-8399-ce3523c6f022" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_06313099-f80a-4a98-9363-d5a5059c9c89" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_05c032eb-40a3-4854-8399-ce3523c6f022" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_06313099-f80a-4a98-9363-d5a5059c9c89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_86ecc548-4d6d-4c31-8289-ce0f63d38996" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_05c032eb-40a3-4854-8399-ce3523c6f022" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_86ecc548-4d6d-4c31-8289-ce0f63d38996" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnDispositionOfAssets1_e6f9dd8c-d8cf-43c8-bf39-61874c786c58" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnDispositionOfAssets1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_05c032eb-40a3-4854-8399-ce3523c6f022" xlink:to="loc_us-gaap_GainLossOnDispositionOfAssets1_e6f9dd8c-d8cf-43c8-bf39-61874c786c58" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_89650130-29d8-47f0-b2a5-95c30dab73f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_05c032eb-40a3-4854-8399-ce3523c6f022" xlink:to="loc_us-gaap_CostsAndExpenses_89650130-29d8-47f0-b2a5-95c30dab73f2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_6ec65ae9-ae01-4d8c-b31b-2a42acdf0ab5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:to="loc_us-gaap_OperatingIncomeLoss_6ec65ae9-ae01-4d8c-b31b-2a42acdf0ab5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_019c4386-2909-71b2-8422-5a8739b53748" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeExpenseNonoperatingNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:to="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_019c4386-2909-71b2-8422-5a8739b53748" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_9e7200f1-d768-4913-81ca-44e7ba08ad8e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_9e7200f1-d768-4913-81ca-44e7ba08ad8e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_25cb4356-a16a-4524-a55d-f4adca4096f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_25cb4356-a16a-4524-a55d-f4adca4096f5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_c9069a84-2bfd-4e98-92e2-f56aebea6598" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_c9069a84-2bfd-4e98-92e2-f56aebea6598" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_e9dbd6ff-2603-47d0-8b0b-1a6e271005cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_e9dbd6ff-2603-47d0-8b0b-1a6e271005cf" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_a8bae692-2718-498b-993e-7641bfa32cc2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:to="loc_us-gaap_ProfitLoss_a8bae692-2718-498b-993e-7641bfa32cc2" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_cc48c229-7df4-449d-8a6c-ffea1745efda" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_cc48c229-7df4-449d-8a6c-ffea1745efda" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_7a8b3acb-85d9-46c7-b9e3-7f6ba5ecc9cd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:to="loc_us-gaap_NetIncomeLoss_7a8b3acb-85d9-46c7-b9e3-7f6ba5ecc9cd" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_1cc73c5f-c79b-481b-86a3-637be3f1f3e9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:to="loc_us-gaap_EarningsPerShareAbstract_1cc73c5f-c79b-481b-86a3-637be3f1f3e9" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_2f57a354-b85e-4d2e-abbd-268b55decb08" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_1cc73c5f-c79b-481b-86a3-637be3f1f3e9" xlink:to="loc_us-gaap_EarningsPerShareBasic_2f57a354-b85e-4d2e-abbd-268b55decb08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_4c00b145-8d7f-46ca-88d6-4a7b0f10ac46" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_1cc73c5f-c79b-481b-86a3-637be3f1f3e9" xlink:to="loc_us-gaap_EarningsPerShareDiluted_4c00b145-8d7f-46ca-88d6-4a7b0f10ac46" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_3eda90f4-3828-464d-8571-734e77e6a05f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2b59c5d9-5c0f-430a-a55d-53d8e2c87a21" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_3eda90f4-3828-464d-8571-734e77e6a05f" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_36e91231-6663-4c1d-b84e-6c70fad19a6c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_3eda90f4-3828-464d-8571-734e77e6a05f" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_36e91231-6663-4c1d-b84e-6c70fad19a6c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_7fb3873b-cfef-4e8c-a5a2-6037024d2293" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasicAbstract_3eda90f4-3828-464d-8571-734e77e6a05f" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_7fb3873b-cfef-4e8c-a5a2-6037024d2293" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/ConsolidatedStatementsofIncomeParenthetical" xlink:type="simple" xlink:href="fi-20251231.xsd#ConsolidatedStatementsofIncomeParenthetical"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/ConsolidatedStatementsofIncomeParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_c285b342-7959-4a8e-91a7-a0bbce5957de" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_2a494c12-dad8-47a3-99f6-682bddff9b1e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_c285b342-7959-4a8e-91a7-a0bbce5957de" xlink:to="loc_us-gaap_StatementTable_2a494c12-dad8-47a3-99f6-682bddff9b1e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_4ffc4445-af7e-4d74-ae47-202a042f8fac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_2a494c12-dad8-47a3-99f6-682bddff9b1e" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_4ffc4445-af7e-4d74-ae47-202a042f8fac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_4ffc4445-af7e-4d74-ae47-202a042f8fac_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_4ffc4445-af7e-4d74-ae47-202a042f8fac" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_4ffc4445-af7e-4d74-ae47-202a042f8fac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_65b67e55-5d93-4022-9a97-222297c9c4d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_4ffc4445-af7e-4d74-ae47-202a042f8fac" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_65b67e55-5d93-4022-9a97-222297c9c4d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_RelatedPartyFeesMember_4ab550eb-b10a-4a61-84dc-724f05e0a67e" xlink:href="fi-20251231.xsd#fi_RelatedPartyFeesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_65b67e55-5d93-4022-9a97-222297c9c4d7" xlink:to="loc_fi_RelatedPartyFeesMember_4ab550eb-b10a-4a61-84dc-724f05e0a67e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_6d84ee4d-4a3d-4f23-8919-a00c1eecce55" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_2a494c12-dad8-47a3-99f6-682bddff9b1e" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_6d84ee4d-4a3d-4f23-8919-a00c1eecce55" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_6d84ee4d-4a3d-4f23-8919-a00c1eecce55_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_6d84ee4d-4a3d-4f23-8919-a00c1eecce55" xlink:to="loc_us-gaap_RelatedPartyDomain_6d84ee4d-4a3d-4f23-8919-a00c1eecce55_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_49d8714c-9a5e-4d38-a0e2-22bda2e8f1d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_6d84ee4d-4a3d-4f23-8919-a00c1eecce55" xlink:to="loc_us-gaap_RelatedPartyDomain_49d8714c-9a5e-4d38-a0e2-22bda2e8f1d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvesteeMember_4fe0b62e-4b7e-48d1-91a8-13c89b765387" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvesteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_49d8714c-9a5e-4d38-a0e2-22bda2e8f1d8" xlink:to="loc_us-gaap_EquityMethodInvesteeMember_4fe0b62e-4b7e-48d1-91a8-13c89b765387" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_a78986cf-36a9-4d27-be51-6f746ba017b8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c285b342-7959-4a8e-91a7-a0bbce5957de" xlink:to="loc_us-gaap_Revenues_a78986cf-36a9-4d27-be51-6f746ba017b8" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/ConsolidatedStatementsofComprehensiveIncome" xlink:type="simple" xlink:href="fi-20251231.xsd#ConsolidatedStatementsofComprehensiveIncome"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/ConsolidatedStatementsofComprehensiveIncome" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_e8b088e7-89e9-4182-80cd-27f9ff9763ad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_7c71e7a2-5fdb-4424-96a1-5cecf10cd3d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_e8b088e7-89e9-4182-80cd-27f9ff9763ad" xlink:to="loc_us-gaap_StatementTable_7c71e7a2-5fdb-4424-96a1-5cecf10cd3d1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_649fbf03-fef3-4041-8d42-4c03f5c45819" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_7c71e7a2-5fdb-4424-96a1-5cecf10cd3d1" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_649fbf03-fef3-4041-8d42-4c03f5c45819" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_649fbf03-fef3-4041-8d42-4c03f5c45819_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_649fbf03-fef3-4041-8d42-4c03f5c45819" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_649fbf03-fef3-4041-8d42-4c03f5c45819_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_69e34d5c-d228-43ba-9adb-a18cec2627da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_649fbf03-fef3-4041-8d42-4c03f5c45819" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_69e34d5c-d228-43ba-9adb-a18cec2627da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_fd1c6345-f2a4-4fa9-a1b1-5313e806e7fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_69e34d5c-d228-43ba-9adb-a18cec2627da" xlink:to="loc_us-gaap_ForeignExchangeContractMember_fd1c6345-f2a4-4fa9-a1b1-5313e806e7fa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryLockMember_89085a59-7f4e-4eb6-8a3d-6f739af6cb1a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryLockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_69e34d5c-d228-43ba-9adb-a18cec2627da" xlink:to="loc_us-gaap_TreasuryLockMember_89085a59-7f4e-4eb6-8a3d-6f739af6cb1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_7d1a21c7-8dbf-4bcb-802c-894ed25d745a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e8b088e7-89e9-4182-80cd-27f9ff9763ad" xlink:to="loc_us-gaap_ProfitLoss_7d1a21c7-8dbf-4bcb-802c-894ed25d745a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_d5157b4d-77f1-4982-8419-9fbcbc0fb91c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e8b088e7-89e9-4182-80cd-27f9ff9763ad" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_d5157b4d-77f1-4982-8419-9fbcbc0fb91c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax_4c789e9e-7020-4b3f-bac6-1c7569e80a82" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_d5157b4d-77f1-4982-8419-9fbcbc0fb91c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax_4c789e9e-7020-4b3f-bac6-1c7569e80a82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax_0a18ebb1-d5fa-4f06-bc1f-5b58a212262d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_d5157b4d-77f1-4982-8419-9fbcbc0fb91c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax_0a18ebb1-d5fa-4f06-bc1f-5b58a212262d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax_1f05a616-e7a1-4982-ab99-54c88f1a5936" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_d5157b4d-77f1-4982-8419-9fbcbc0fb91c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax_1f05a616-e7a1-4982-ab99-54c88f1a5936" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax_36677dc0-67b7-4f20-afac-b09cab5749a2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_d5157b4d-77f1-4982-8419-9fbcbc0fb91c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax_36677dc0-67b7-4f20-afac-b09cab5749a2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax_120b91d0-b229-418f-b447-05342c661211" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_d5157b4d-77f1-4982-8419-9fbcbc0fb91c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax_120b91d0-b229-418f-b447-05342c661211" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax_ac0fb102-3d7e-428a-bf87-207fcf6d74a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_d5157b4d-77f1-4982-8419-9fbcbc0fb91c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax_ac0fb102-3d7e-428a-bf87-207fcf6d74a4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax_d4761d98-e0c6-4c2a-9256-efee9bf56d4a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_d5157b4d-77f1-4982-8419-9fbcbc0fb91c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossBeforeReclassificationAndTax_d4761d98-e0c6-4c2a-9256-efee9bf56d4a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationBeforeTax_ddfec470-514b-4160-9500-2ca9a167481c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_d5157b4d-77f1-4982-8419-9fbcbc0fb91c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationBeforeTax_ddfec470-514b-4160-9500-2ca9a167481c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_de2597d7-e20a-4ff6-8330-f4f0667399d7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_d5157b4d-77f1-4982-8419-9fbcbc0fb91c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_de2597d7-e20a-4ff6-8330-f4f0667399d7" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_c1b9817f-a425-41cd-9fb0-7303eb01fcbe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_d5157b4d-77f1-4982-8419-9fbcbc0fb91c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_c1b9817f-a425-41cd-9fb0-7303eb01fcbe" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_73e69b44-b35e-427d-a5ab-4f7fe609344b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e8b088e7-89e9-4182-80cd-27f9ff9763ad" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_73e69b44-b35e-427d-a5ab-4f7fe609344b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_00902d9c-df58-40f3-8ad5-01ff3ea96c34" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e8b088e7-89e9-4182-80cd-27f9ff9763ad" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_00902d9c-df58-40f3-8ad5-01ff3ea96c34" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest_65c33b6b-156f-4df6-85a2-94fc98edbc2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e8b088e7-89e9-4182-80cd-27f9ff9763ad" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest_65c33b6b-156f-4df6-85a2-94fc98edbc2c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_f34dcf99-c82f-4b42-830c-85ce71cb42eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e8b088e7-89e9-4182-80cd-27f9ff9763ad" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_f34dcf99-c82f-4b42-830c-85ce71cb42eb" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/ConsolidatedBalanceSheets" xlink:type="simple" xlink:href="fi-20251231.xsd#ConsolidatedBalanceSheets"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/ConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_14ee5c28-f7d4-46e1-9a8b-e7594aab8c18" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_49ceab2a-ee95-4edc-9d9e-0c70c48c23e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_14ee5c28-f7d4-46e1-9a8b-e7594aab8c18" xlink:to="loc_us-gaap_StatementTable_49ceab2a-ee95-4edc-9d9e-0c70c48c23e8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7d6a76f9-1dae-4405-a821-0669e5f41ad6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_49ceab2a-ee95-4edc-9d9e-0c70c48c23e8" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7d6a76f9-1dae-4405-a821-0669e5f41ad6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_7d6a76f9-1dae-4405-a821-0669e5f41ad6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7d6a76f9-1dae-4405-a821-0669e5f41ad6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_7d6a76f9-1dae-4405-a821-0669e5f41ad6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_77b3e793-3382-4bc3-80fe-e30dbb21ebd9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_7d6a76f9-1dae-4405-a821-0669e5f41ad6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_77b3e793-3382-4bc3-80fe-e30dbb21ebd9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_a516acf2-efdc-473f-a57a-3b1dcc5fc244" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerRelatedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_77b3e793-3382-4bc3-80fe-e30dbb21ebd9" xlink:to="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_a516acf2-efdc-473f-a57a-3b1dcc5fc244" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_2ed4c81d-7990-4c5e-8ae3-d25b4839364c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_77b3e793-3382-4bc3-80fe-e30dbb21ebd9" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_2ed4c81d-7990-4c5e-8ae3-d25b4839364c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_a42df254-af33-4645-8000-11f893849fbe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_14ee5c28-f7d4-46e1-9a8b-e7594aab8c18" xlink:to="loc_us-gaap_AssetsAbstract_a42df254-af33-4645-8000-11f893849fbe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_00c64e81-d014-4bf1-8c42-02597380f714" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a42df254-af33-4645-8000-11f893849fbe" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_00c64e81-d014-4bf1-8c42-02597380f714" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_651db988-c546-4e65-9fff-aa22aa72dc09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a42df254-af33-4645-8000-11f893849fbe" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_651db988-c546-4e65-9fff-aa22aa72dc09" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_dd96475d-1efb-4742-a311-381634630845" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a42df254-af33-4645-8000-11f893849fbe" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_dd96475d-1efb-4742-a311-381634630845" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SettlementAssetsCurrent_9d854285-5094-4c4f-a467-debb8237f232" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SettlementAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a42df254-af33-4645-8000-11f893849fbe" xlink:to="loc_us-gaap_SettlementAssetsCurrent_9d854285-5094-4c4f-a467-debb8237f232" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_2888aca1-b0a9-4cee-b62b-c1d753339a5d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a42df254-af33-4645-8000-11f893849fbe" xlink:to="loc_us-gaap_AssetsCurrent_2888aca1-b0a9-4cee-b62b-c1d753339a5d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_3311a3a8-f6bd-43bd-9bd9-1fc323db5110" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a42df254-af33-4645-8000-11f893849fbe" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_3311a3a8-f6bd-43bd-9bd9-1fc323db5110" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_cd15dc95-68a7-4c57-81e0-7491bcb7edf0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a42df254-af33-4645-8000-11f893849fbe" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_cd15dc95-68a7-4c57-81e0-7491bcb7edf0" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_2c0850f8-4837-4a6f-9321-b8bafd2d9208" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a42df254-af33-4645-8000-11f893849fbe" xlink:to="loc_us-gaap_Goodwill_2c0850f8-4837-4a6f-9321-b8bafd2d9208" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostNet_39e029fb-0c10-42cf-a4ea-165380aac44a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalizedContractCostNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a42df254-af33-4645-8000-11f893849fbe" xlink:to="loc_us-gaap_CapitalizedContractCostNet_39e029fb-0c10-42cf-a4ea-165380aac44a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_540cdb4b-4231-4e96-9687-8547672af528" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a42df254-af33-4645-8000-11f893849fbe" xlink:to="loc_us-gaap_EquityMethodInvestments_540cdb4b-4231-4e96-9687-8547672af528" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_007b8363-cb7a-42ea-97f9-f3e2be962462" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a42df254-af33-4645-8000-11f893849fbe" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_007b8363-cb7a-42ea-97f9-f3e2be962462" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_f115a47a-0e67-46a0-a68d-6393ed336002" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_a42df254-af33-4645-8000-11f893849fbe" xlink:to="loc_us-gaap_Assets_f115a47a-0e67-46a0-a68d-6393ed336002" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_14ee5c28-f7d4-46e1-9a8b-e7594aab8c18" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_604de7fe-1411-4fdb-a481-4f5974319cac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_604de7fe-1411-4fdb-a481-4f5974319cac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent_5e3cafd2-d2ea-4824-9e47-500782f15cba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent_5e3cafd2-d2ea-4824-9e47-500782f15cba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_fa4af44e-148f-4dd8-a41b-fec95b31e03a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_fa4af44e-148f-4dd8-a41b-fec95b31e03a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SettlementLiabilitiesCurrent_c11b5e48-3ed0-4176-9875-708f699d1a0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SettlementLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_SettlementLiabilitiesCurrent_c11b5e48-3ed0-4176-9875-708f699d1a0b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_c0b7846f-671b-4eca-a1bf-72cf06a4fec4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_LiabilitiesCurrent_c0b7846f-671b-4eca-a1bf-72cf06a4fec4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_edacb43d-4102-40ef-b1dd-60dd74b55264" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_edacb43d-4102-40ef-b1dd-60dd74b55264" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_aa2f6240-cc49-47a9-9bef-e7d29df1896d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_aa2f6240-cc49-47a9-9bef-e7d29df1896d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_d6995e97-8c09-4f11-8cfd-1ee2803aaaa9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_d6995e97-8c09-4f11-8cfd-1ee2803aaaa9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_f44647fa-bb86-4f9a-97e9-d022b157bc0a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_f44647fa-bb86-4f9a-97e9-d022b157bc0a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_6474a4d2-13cf-45e0-bc70-365f7e120e57" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_Liabilities_6474a4d2-13cf-45e0-bc70-365f7e120e57" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_2a500335-6fe3-49be-a799-83c0e141e9a5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_CommitmentsAndContingencies_2a500335-6fe3-49be-a799-83c0e141e9a5" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityAbstract_2544d1e7-2591-44a8-88bb-852f08e0d8c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_StockholdersEquityAbstract_2544d1e7-2591-44a8-88bb-852f08e0d8c3" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PreferredStockValue_b7d30f78-ffb2-46f3-9e41-018c22414332" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PreferredStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_2544d1e7-2591-44a8-88bb-852f08e0d8c3" xlink:to="loc_us-gaap_PreferredStockValue_b7d30f78-ffb2-46f3-9e41-018c22414332" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValueOutstanding_5837cdc0-f51f-4b50-b0c5-ea861d350c09" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockValueOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_2544d1e7-2591-44a8-88bb-852f08e0d8c3" xlink:to="loc_us-gaap_CommonStockValueOutstanding_5837cdc0-f51f-4b50-b0c5-ea861d350c09" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_1db4f2c0-c421-44bc-be47-183ae315c5cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_2544d1e7-2591-44a8-88bb-852f08e0d8c3" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_1db4f2c0-c421-44bc-be47-183ae315c5cb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_6913a58b-351a-4a08-a0e2-2019b50d9f48" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_2544d1e7-2591-44a8-88bb-852f08e0d8c3" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_6913a58b-351a-4a08-a0e2-2019b50d9f48" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_5c84ae2b-b65b-4ee6-b38b-2e6c7cf2ac71" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_2544d1e7-2591-44a8-88bb-852f08e0d8c3" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_5c84ae2b-b65b-4ee6-b38b-2e6c7cf2ac71" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonValue_0b42aa38-773e-4cd6-88f6-3e34595d0f08" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_2544d1e7-2591-44a8-88bb-852f08e0d8c3" xlink:to="loc_us-gaap_TreasuryStockCommonValue_0b42aa38-773e-4cd6-88f6-3e34595d0f08" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_c4f1bcc6-b174-49e2-84c2-c2b04df63058" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_2544d1e7-2591-44a8-88bb-852f08e0d8c3" xlink:to="loc_us-gaap_StockholdersEquity_c4f1bcc6-b174-49e2-84c2-c2b04df63058" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterest_4c72893a-cedf-482f-85d0-c93dad464577" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_MinorityInterest_4c72893a-cedf-482f-85d0-c93dad464577" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_310a45d6-a7c7-4734-bd02-9805d9116fae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_310a45d6-a7c7-4734-bd02-9805d9116fae" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_e46a2bcf-0d7d-4736-9965-58a66ad185d4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_88008d19-8c9d-4595-8199-d8989e0d08b4" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_e46a2bcf-0d7d-4736-9965-58a66ad185d4" xlink:type="arc" order="15"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/ConsolidatedStatementsofEquity" xlink:type="simple" xlink:href="fi-20251231.xsd#ConsolidatedStatementsofEquity"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/ConsolidatedStatementsofEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_42a7da96-0151-4b81-8d55-5a76c9faa43e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_1a7633c7-7cb1-4520-84b0-b1e572678143" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_42a7da96-0151-4b81-8d55-5a76c9faa43e" xlink:to="loc_us-gaap_StatementTable_1a7633c7-7cb1-4520-84b0-b1e572678143" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_828c50ee-391d-4ee0-a460-6970b4ff3a6b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1a7633c7-7cb1-4520-84b0-b1e572678143" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_828c50ee-391d-4ee0-a460-6970b4ff3a6b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_828c50ee-391d-4ee0-a460-6970b4ff3a6b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_828c50ee-391d-4ee0-a460-6970b4ff3a6b" xlink:to="loc_us-gaap_EquityComponentDomain_828c50ee-391d-4ee0-a460-6970b4ff3a6b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_c28a94bd-fc5e-4021-b751-589c101a6c55" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_828c50ee-391d-4ee0-a460-6970b4ff3a6b" xlink:to="loc_us-gaap_EquityComponentDomain_c28a94bd-fc5e-4021-b751-589c101a6c55" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_61d996ee-5441-43a5-91d3-87ad13ac8b3a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c28a94bd-fc5e-4021-b751-589c101a6c55" xlink:to="loc_us-gaap_CommonStockMember_61d996ee-5441-43a5-91d3-87ad13ac8b3a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_47cbc64f-577c-4c18-a7f6-8746c44b0264" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c28a94bd-fc5e-4021-b751-589c101a6c55" xlink:to="loc_us-gaap_TreasuryStockCommonMember_47cbc64f-577c-4c18-a7f6-8746c44b0264" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_56f4dff6-a18f-4d21-af17-25e802739fb4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c28a94bd-fc5e-4021-b751-589c101a6c55" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_56f4dff6-a18f-4d21-af17-25e802739fb4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_bf014b1c-6ab4-450b-911e-e5e6ead28776" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c28a94bd-fc5e-4021-b751-589c101a6c55" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_bf014b1c-6ab4-450b-911e-e5e6ead28776" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_25c7f527-232b-42b9-8402-22ff5251adf5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c28a94bd-fc5e-4021-b751-589c101a6c55" xlink:to="loc_us-gaap_RetainedEarningsMember_25c7f527-232b-42b9-8402-22ff5251adf5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_1201981d-15ce-411e-8b85-f07355197810" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c28a94bd-fc5e-4021-b751-589c101a6c55" xlink:to="loc_us-gaap_NoncontrollingInterestMember_1201981d-15ce-411e-8b85-f07355197810" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_42a7da96-0151-4b81-8d55-5a76c9faa43e" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_85d7a248-62ab-4c1f-b9a8-f7c846007a40" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_85d7a248-62ab-4c1f-b9a8-f7c846007a40" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_5b7124c2-ca0f-4d30-9ce8-4f5b04bf7fc2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:to="loc_us-gaap_TreasuryStockCommonShares_5b7124c2-ca0f-4d30-9ce8-4f5b04bf7fc2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_2d83fcb0-7dd8-461c-9a0f-f86f2997e815" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_2d83fcb0-7dd8-461c-9a0f-f86f2997e815" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest_d0aa58b2-e09f-4197-a2af-0d4e9efd48b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:to="loc_us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest_d0aa58b2-e09f-4197-a2af-0d4e9efd48b4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_e7777ada-5550-43cd-82ee-5052197e3850" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_e7777ada-5550-43cd-82ee-5052197e3850" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_IncreaseDecreaseFromAcquisitionOfNoncontrollingInterestOfConsolidatedSubsidiary_6b8ebf8d-d2d2-4c30-b662-bd0e6da3cf12" xlink:href="fi-20251231.xsd#fi_IncreaseDecreaseFromAcquisitionOfNoncontrollingInterestOfConsolidatedSubsidiary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:to="loc_fi_IncreaseDecreaseFromAcquisitionOfNoncontrollingInterestOfConsolidatedSubsidiary_6b8ebf8d-d2d2-4c30-b662-bd0e6da3cf12" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestChangeInRedemptionValue_1772cffe-6337-4bb1-97be-2eebf5a2191f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterestChangeInRedemptionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:to="loc_us-gaap_MinorityInterestChangeInRedemptionValue_1772cffe-6337-4bb1-97be-2eebf5a2191f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_ca7d85f2-0787-48ae-8d51-dcd873c28376" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_ca7d85f2-0787-48ae-8d51-dcd873c28376" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_b08bda07-f63d-4c16-81ad-bac693fd63e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_b08bda07-f63d-4c16-81ad-bac693fd63e2" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_b957ee63-70bf-4847-bfad-f9900c1d7ca6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_b957ee63-70bf-4847-bfad-f9900c1d7ca6" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_f20b9e30-55d8-4d6f-b6e7-064001d00dcb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_f20b9e30-55d8-4d6f-b6e7-064001d00dcb" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_656dbcee-67e6-47d9-9982-1cb1085cbd56" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_656dbcee-67e6-47d9-9982-1cb1085cbd56" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_9d21bada-c6fe-4daf-86d5-c693e7dfe7ce" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_9d21bada-c6fe-4daf-86d5-c693e7dfe7ce" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance_b697921b-89a3-4035-8e92-d41544284217" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_fc0eaa9c-46c1-491a-8cff-b740c681b355" xlink:to="loc_us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance_b697921b-89a3-4035-8e92-d41544284217" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_bd7fe632-93ef-42ba-8836-38f9f0b42130" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_284b1b4d-d112-4a76-a37c-2ec72a33d98a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_828dcdc1-7f70-40d9-b669-1165388de7cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/ConsolidatedStatementsofEquityParenthetical" xlink:type="simple" xlink:href="fi-20251231.xsd#ConsolidatedStatementsofEquityParenthetical"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/ConsolidatedStatementsofEquityParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_eab2182b-cad4-4e9c-802f-d7aaa461a4a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_88fa475c-5133-4490-ae7f-0c9d4a34ef75" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_eab2182b-cad4-4e9c-802f-d7aaa461a4a6" xlink:to="loc_us-gaap_StatementTable_88fa475c-5133-4490-ae7f-0c9d4a34ef75" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_4a994da8-16be-4ab3-8110-13f9793b5a20" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_88fa475c-5133-4490-ae7f-0c9d4a34ef75" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_4a994da8-16be-4ab3-8110-13f9793b5a20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4a994da8-16be-4ab3-8110-13f9793b5a20_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_4a994da8-16be-4ab3-8110-13f9793b5a20" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4a994da8-16be-4ab3-8110-13f9793b5a20_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_041e9e1e-ced0-489f-8e90-80b52a11dc99" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_4a994da8-16be-4ab3-8110-13f9793b5a20" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_041e9e1e-ced0-489f-8e90-80b52a11dc99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_EuropeanMerchantServicesBVMember_60289cf3-9d0d-4b35-921b-8262cfde8539" xlink:href="fi-20251231.xsd#fi_EuropeanMerchantServicesBVMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_041e9e1e-ced0-489f-8e90-80b52a11dc99" xlink:to="loc_fi_EuropeanMerchantServicesBVMember_60289cf3-9d0d-4b35-921b-8262cfde8539" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_ICICIMerchantServicesPrivateLimitedMember_1b03ae22-3ad1-43c2-81aa-58a46ac6e703" xlink:href="fi-20251231.xsd#fi_ICICIMerchantServicesPrivateLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_041e9e1e-ced0-489f-8e90-80b52a11dc99" xlink:to="loc_fi_ICICIMerchantServicesPrivateLimitedMember_1b03ae22-3ad1-43c2-81aa-58a46ac6e703" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_AIBMSMember_0fa43480-8774-4f80-ad46-dd11c75ecbd8" xlink:href="fi-20251231.xsd#fi_AIBMSMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_041e9e1e-ced0-489f-8e90-80b52a11dc99" xlink:to="loc_fi_AIBMSMember_0fa43480-8774-4f80-ad46-dd11c75ecbd8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToRedeemableNoncontrollingInterest_1a2f1d59-729e-4c72-9540-217924141991" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLossAttributableToRedeemableNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_eab2182b-cad4-4e9c-802f-d7aaa461a4a6" xlink:to="loc_us-gaap_NetIncomeLossAttributableToRedeemableNoncontrollingInterest_1a2f1d59-729e-4c72-9540-217924141991" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_NoncontrollingInterestDecreaseFromDistributionsToRedeemableNoncontrollingInterestHolders_2d26ce66-e730-4b94-8ff9-f865bd340b53" xlink:href="fi-20251231.xsd#fi_NoncontrollingInterestDecreaseFromDistributionsToRedeemableNoncontrollingInterestHolders"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_eab2182b-cad4-4e9c-802f-d7aaa461a4a6" xlink:to="loc_fi_NoncontrollingInterestDecreaseFromDistributionsToRedeemableNoncontrollingInterestHolders_2d26ce66-e730-4b94-8ff9-f865bd340b53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_5281190f-6474-4054-a29b-8345bf6ce5e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_eab2182b-cad4-4e9c-802f-d7aaa461a4a6" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_5281190f-6474-4054-a29b-8345bf6ce5e5" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/SummaryofSignificantAccountingPoliciesPrepaidExpensesDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#SummaryofSignificantAccountingPoliciesPrepaidExpensesDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/SummaryofSignificantAccountingPoliciesPrepaidExpensesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_99c79635-bc20-45ac-bbcc-887abaf22d38" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_b6386766-dc61-41bc-93ad-f7d9383f6d9f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_99c79635-bc20-45ac-bbcc-887abaf22d38" xlink:to="loc_us-gaap_LossContingenciesTable_b6386766-dc61-41bc-93ad-f7d9383f6d9f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_c106458d-597f-42e1-a511-10e590294117" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_b6386766-dc61-41bc-93ad-f7d9383f6d9f" xlink:to="loc_srt_CounterpartyNameAxis_c106458d-597f-42e1-a511-10e590294117" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_c106458d-597f-42e1-a511-10e590294117_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_c106458d-597f-42e1-a511-10e590294117" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_c106458d-597f-42e1-a511-10e590294117_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_5e1dfdff-c046-4993-bf52-f7bc84ecfbad" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_c106458d-597f-42e1-a511-10e590294117" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_5e1dfdff-c046-4993-bf52-f7bc84ecfbad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_CloverCapitalMember_8f0d683f-429f-42b3-bd39-3b3bdbf69b0d" xlink:href="fi-20251231.xsd#fi_CloverCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_5e1dfdff-c046-4993-bf52-f7bc84ecfbad" xlink:to="loc_fi_CloverCapitalMember_8f0d683f-429f-42b3-bd39-3b3bdbf69b0d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_ForeignMerchantsMember_019b0dfb-c980-71c6-869b-56f5424d7be4" xlink:href="fi-20251231.xsd#fi_ForeignMerchantsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_5e1dfdff-c046-4993-bf52-f7bc84ecfbad" xlink:to="loc_fi_ForeignMerchantsMember_019b0dfb-c980-71c6-869b-56f5424d7be4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_MerchantsUtilizingCloverCapitalCashAdvanceProgramMember_69e99428-b8ae-4e48-b0b1-256581f7c9f9" xlink:href="fi-20251231.xsd#fi_MerchantsUtilizingCloverCapitalCashAdvanceProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_5e1dfdff-c046-4993-bf52-f7bc84ecfbad" xlink:to="loc_fi_MerchantsUtilizingCloverCapitalCashAdvanceProgramMember_69e99428-b8ae-4e48-b0b1-256581f7c9f9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019c28f6-d615-7511-bc7a-71e4eec53cc3" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_b6386766-dc61-41bc-93ad-f7d9383f6d9f" xlink:to="loc_srt_RangeAxis_019c28f6-d615-7511-bc7a-71e4eec53cc3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c28f6-d615-7511-bc7a-71e4eec53cc3_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019c28f6-d615-7511-bc7a-71e4eec53cc3" xlink:to="loc_srt_RangeMember_019c28f6-d615-7511-bc7a-71e4eec53cc3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019c28f6-d615-741c-8152-0af52da3ab8a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019c28f6-d615-7511-bc7a-71e4eec53cc3" xlink:to="loc_srt_RangeMember_019c28f6-d615-741c-8152-0af52da3ab8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019c28f6-eddf-7a53-8ede-ac3fbb45f975" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019c28f6-d615-741c-8152-0af52da3ab8a" xlink:to="loc_srt_MinimumMember_019c28f6-eddf-7a53-8ede-ac3fbb45f975" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019c28f6-fd03-7ada-9bbc-bd0154ad4c99" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019c28f6-d615-741c-8152-0af52da3ab8a" xlink:to="loc_srt_MaximumMember_019c28f6-fd03-7ada-9bbc-bd0154ad4c99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_PrepaidMaintenancePostageAndInsurance_cdee4054-8192-4c71-9ddb-f6990d424e92" xlink:href="fi-20251231.xsd#fi_PrepaidMaintenancePostageAndInsurance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_99c79635-bc20-45ac-bbcc-887abaf22d38" xlink:to="loc_fi_PrepaidMaintenancePostageAndInsurance_cdee4054-8192-4c71-9ddb-f6990d424e92" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPrepaidExpenseCurrent_c49c19d6-2c09-4efc-bdf1-f902da18072f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherPrepaidExpenseCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_99c79635-bc20-45ac-bbcc-887abaf22d38" xlink:to="loc_us-gaap_OtherPrepaidExpenseCurrent_c49c19d6-2c09-4efc-bdf1-f902da18072f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseCurrent_b644a5bb-ea8d-4b09-ba9f-d6c54bfd4fec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepaidExpenseCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_99c79635-bc20-45ac-bbcc-887abaf22d38" xlink:to="loc_us-gaap_PrepaidExpenseCurrent_b644a5bb-ea8d-4b09-ba9f-d6c54bfd4fec" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesReceivable_1d3a69e5-0627-4439-ac57-679c341962b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxesReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_99c79635-bc20-45ac-bbcc-887abaf22d38" xlink:to="loc_us-gaap_IncomeTaxesReceivable_1d3a69e5-0627-4439-ac57-679c341962b5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossCurrent_00d073cc-2b5a-480b-b8b1-6e668552d98b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_99c79635-bc20-45ac-bbcc-887abaf22d38" xlink:to="loc_us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLossCurrent_00d073cc-2b5a-480b-b8b1-6e668552d98b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsMiscellaneousCurrent_a9ad0b4d-04e3-46ea-80e1-5ddcb1cf695f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsMiscellaneousCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_99c79635-bc20-45ac-bbcc-887abaf22d38" xlink:to="loc_us-gaap_OtherAssetsMiscellaneousCurrent_a9ad0b4d-04e3-46ea-80e1-5ddcb1cf695f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsCurrent_1618689d-02f8-46a5-9717-7920dc3fd721" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_99c79635-bc20-45ac-bbcc-887abaf22d38" xlink:to="loc_us-gaap_OtherAssetsCurrent_1618689d-02f8-46a5-9717-7920dc3fd721" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_50dafcbe-1fd8-407f-9f38-9eeae13a3378" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_99c79635-bc20-45ac-bbcc-887abaf22d38" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_50dafcbe-1fd8-407f-9f38-9eeae13a3378" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterestCurrent_58821575-b3ab-46c8-9717-400ddeccd8aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterestCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_99c79635-bc20-45ac-bbcc-887abaf22d38" xlink:to="loc_us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterestCurrent_58821575-b3ab-46c8-9717-400ddeccd8aa" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_FinancingReceivableMerchantCashAdvancesCollectionPeriod_019be689-d33d-76b5-a03b-992f93388026" xlink:href="fi-20251231.xsd#fi_FinancingReceivableMerchantCashAdvancesCollectionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_99c79635-bc20-45ac-bbcc-887abaf22d38" xlink:to="loc_fi_FinancingReceivableMerchantCashAdvancesCollectionPeriod_019be689-d33d-76b5-a03b-992f93388026" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_SettlementAnticipationCashAdvancesCollectionPeriod_019c199f-27cb-70c6-9513-9ad6266ee0a8" xlink:href="fi-20251231.xsd#fi_SettlementAnticipationCashAdvancesCollectionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_99c79635-bc20-45ac-bbcc-887abaf22d38" xlink:to="loc_fi_SettlementAnticipationCashAdvancesCollectionPeriod_019c199f-27cb-70c6-9513-9ad6266ee0a8" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/SummaryofSignificantAccountingPoliciesAllowanceforMerchantCreditLossesDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#SummaryofSignificantAccountingPoliciesAllowanceforMerchantCreditLossesDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/SummaryofSignificantAccountingPoliciesAllowanceforMerchantCreditLossesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_c1162964-ba27-4cf5-9425-d4260669e238" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_cc006952-1828-48c8-b468-f9018a31d48b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_c1162964-ba27-4cf5-9425-d4260669e238" xlink:to="loc_us-gaap_LossContingenciesTable_cc006952-1828-48c8-b468-f9018a31d48b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_9710b17e-1791-4774-b229-46e82ba22492" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesByNatureOfContingencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_cc006952-1828-48c8-b468-f9018a31d48b" xlink:to="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_9710b17e-1791-4774-b229-46e82ba22492" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_9710b17e-1791-4774-b229-46e82ba22492_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_9710b17e-1791-4774-b229-46e82ba22492" xlink:to="loc_us-gaap_LossContingencyNatureDomain_9710b17e-1791-4774-b229-46e82ba22492_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyNatureDomain_c10d62e5-2d71-44c4-bb29-d237a00d08fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LossContingenciesByNatureOfContingencyAxis_9710b17e-1791-4774-b229-46e82ba22492" xlink:to="loc_us-gaap_LossContingencyNatureDomain_c10d62e5-2d71-44c4-bb29-d237a00d08fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_MerchantCreditLossesMember_8e565caf-0371-4611-b3b5-4dd89a456f02" xlink:href="fi-20251231.xsd#fi_MerchantCreditLossesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingencyNatureDomain_c10d62e5-2d71-44c4-bb29-d237a00d08fa" xlink:to="loc_fi_MerchantCreditLossesMember_8e565caf-0371-4611-b3b5-4dd89a456f02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_LossContingencyCollateralHeld_fb29a631-b1bb-4537-bc28-9606940ec16f" xlink:href="fi-20251231.xsd#fi_LossContingencyCollateralHeld"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c1162964-ba27-4cf5-9425-d4260669e238" xlink:to="loc_fi_LossContingencyCollateralHeld_fb29a631-b1bb-4537-bc28-9606940ec16f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyLossInPeriod_9ff71ed5-df89-4a01-87cb-877f66f1afa9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyLossInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c1162964-ba27-4cf5-9425-d4260669e238" xlink:to="loc_us-gaap_LossContingencyLossInPeriod_9ff71ed5-df89-4a01-87cb-877f66f1afa9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_b992fef6-6ff6-4505-9f23-edecf535af0d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_c1162964-ba27-4cf5-9425-d4260669e238" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_b992fef6-6ff6-4505-9f23-edecf535af0d" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/SummaryofSignificantAccountingPoliciesPropertyandEquipmentDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#SummaryofSignificantAccountingPoliciesPropertyandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/SummaryofSignificantAccountingPoliciesPropertyandEquipmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_c6887a30-1105-48f2-b1e4-723f591c2236" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_3693a6f3-4cb2-4ebb-a8e7-8bf7b622077d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_c6887a30-1105-48f2-b1e4-723f591c2236" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_3693a6f3-4cb2-4ebb-a8e7-8bf7b622077d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e67c52c6-5847-4cbd-bcdc-a773145bd33b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_3693a6f3-4cb2-4ebb-a8e7-8bf7b622077d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e67c52c6-5847-4cbd-bcdc-a773145bd33b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e67c52c6-5847-4cbd-bcdc-a773145bd33b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e67c52c6-5847-4cbd-bcdc-a773145bd33b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_e67c52c6-5847-4cbd-bcdc-a773145bd33b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_594aa1e1-d2bd-4882-8bf3-9b1b0ca4f03d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_e67c52c6-5847-4cbd-bcdc-a773145bd33b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_594aa1e1-d2bd-4882-8bf3-9b1b0ca4f03d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandMember_733b70dc-a7c8-498a-afd6-3a3863baee8c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LandMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_594aa1e1-d2bd-4882-8bf3-9b1b0ca4f03d" xlink:to="loc_us-gaap_LandMember_733b70dc-a7c8-498a-afd6-3a3863baee8c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_DataProcessingEquipmentMember_e471dc2f-69a1-4977-8027-532b0b213368" xlink:href="fi-20251231.xsd#fi_DataProcessingEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_594aa1e1-d2bd-4882-8bf3-9b1b0ca4f03d" xlink:to="loc_fi_DataProcessingEquipmentMember_e471dc2f-69a1-4977-8027-532b0b213368" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_BuildingsAndLeaseholdImprovementsMember_4a848b86-3ffb-47f3-8498-d4b9819a51f3" xlink:href="fi-20251231.xsd#fi_BuildingsAndLeaseholdImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_594aa1e1-d2bd-4882-8bf3-9b1b0ca4f03d" xlink:to="loc_fi_BuildingsAndLeaseholdImprovementsMember_4a848b86-3ffb-47f3-8498-d4b9819a51f3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_FurnitureAndEquipmentMember_9396ab0f-f6ce-4faf-bde1-1c84de2f0533" xlink:href="fi-20251231.xsd#fi_FurnitureAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_594aa1e1-d2bd-4882-8bf3-9b1b0ca4f03d" xlink:to="loc_fi_FurnitureAndEquipmentMember_9396ab0f-f6ce-4faf-bde1-1c84de2f0533" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_1f84df30-0b12-46e9-9f7f-ead84dfb4af8" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_3693a6f3-4cb2-4ebb-a8e7-8bf7b622077d" xlink:to="loc_srt_RangeAxis_1f84df30-0b12-46e9-9f7f-ead84dfb4af8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_1f84df30-0b12-46e9-9f7f-ead84dfb4af8_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_1f84df30-0b12-46e9-9f7f-ead84dfb4af8" xlink:to="loc_srt_RangeMember_1f84df30-0b12-46e9-9f7f-ead84dfb4af8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_fa12395a-cc8a-4412-82d5-3bbda1fc0fdc" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_1f84df30-0b12-46e9-9f7f-ead84dfb4af8" xlink:to="loc_srt_RangeMember_fa12395a-cc8a-4412-82d5-3bbda1fc0fdc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_7bb7fdc0-b5e6-4310-beb5-56d83ee5ae34" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_fa12395a-cc8a-4412-82d5-3bbda1fc0fdc" xlink:to="loc_srt_MinimumMember_7bb7fdc0-b5e6-4310-beb5-56d83ee5ae34" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_1bf5ff7a-f7de-49a8-b1e5-c884054d8cd3" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_fa12395a-cc8a-4412-82d5-3bbda1fc0fdc" xlink:to="loc_srt_MaximumMember_1bf5ff7a-f7de-49a8-b1e5-c884054d8cd3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_65dd28b0-971d-4231-b151-3515aba0dd40" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_c6887a30-1105-48f2-b1e4-723f591c2236" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_65dd28b0-971d-4231-b151-3515aba0dd40" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_5275251c-3274-40e5-a5fc-29c0c381eca1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_c6887a30-1105-48f2-b1e4-723f591c2236" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetBeforeAccumulatedDepreciationAndAmortization_5275251c-3274-40e5-a5fc-29c0c381eca1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_86dad41c-4962-4b6e-acc4-f6b1dda8a22e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_c6887a30-1105-48f2-b1e4-723f591c2236" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAccumulatedDepreciationAndAmortization_86dad41c-4962-4b6e-acc4-f6b1dda8a22e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_0e593998-7c99-4aac-b7a2-fe6c4e544ea8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_c6887a30-1105-48f2-b1e4-723f591c2236" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization_0e593998-7c99-4aac-b7a2-fe6c4e544ea8" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/SummaryofSignificantAccountingPoliciesIntangibleAssetsDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#SummaryofSignificantAccountingPoliciesIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/SummaryofSignificantAccountingPoliciesIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_c76061ef-97c3-4a06-9607-17e44166a01a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_5cd74d42-4214-42bc-90d6-8a291cbf4950" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_c76061ef-97c3-4a06-9607-17e44166a01a" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_5cd74d42-4214-42bc-90d6-8a291cbf4950" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_4684f7aa-dbfa-46d1-ad3e-a6b2d3c9abde" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_5cd74d42-4214-42bc-90d6-8a291cbf4950" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_4684f7aa-dbfa-46d1-ad3e-a6b2d3c9abde" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_4684f7aa-dbfa-46d1-ad3e-a6b2d3c9abde_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_4684f7aa-dbfa-46d1-ad3e-a6b2d3c9abde" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_4684f7aa-dbfa-46d1-ad3e-a6b2d3c9abde_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f9294e44-e651-45fd-a3d4-08dc32612558" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_4684f7aa-dbfa-46d1-ad3e-a6b2d3c9abde" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f9294e44-e651-45fd-a3d4-08dc32612558" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_f3b1f7c8-ac46-4e3a-8997-468294ed9532" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerRelatedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f9294e44-e651-45fd-a3d4-08dc32612558" xlink:to="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_f3b1f7c8-ac46-4e3a-8997-468294ed9532" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_AcquiredSoftwareAndTechnologyMember_da96d65e-1caf-4408-87a1-77c4188bf1ac" xlink:href="fi-20251231.xsd#fi_AcquiredSoftwareAndTechnologyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f9294e44-e651-45fd-a3d4-08dc32612558" xlink:to="loc_fi_AcquiredSoftwareAndTechnologyMember_da96d65e-1caf-4408-87a1-77c4188bf1ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_82ae698e-7363-457c-b61d-e4f95c0f8c4f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f9294e44-e651-45fd-a3d4-08dc32612558" xlink:to="loc_us-gaap_TradeNamesMember_82ae698e-7363-457c-b61d-e4f95c0f8c4f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_NonCompeteAgreementMember_3c699f47-b154-4662-a81d-47acc205bf5f" xlink:href="fi-20251231.xsd#fi_NonCompeteAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f9294e44-e651-45fd-a3d4-08dc32612558" xlink:to="loc_fi_NonCompeteAgreementMember_3c699f47-b154-4662-a81d-47acc205bf5f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_4032997e-a179-4d3f-a270-3f1ec4b9cc2f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComputerSoftwareIntangibleAssetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f9294e44-e651-45fd-a3d4-08dc32612558" xlink:to="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_4032997e-a179-4d3f-a270-3f1ec4b9cc2f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_CapitalizedSoftwareDevelopmentCostsMember_2d3ea3d7-d188-46dd-aac5-5fda4207a244" xlink:href="fi-20251231.xsd#fi_CapitalizedSoftwareDevelopmentCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f9294e44-e651-45fd-a3d4-08dc32612558" xlink:to="loc_fi_CapitalizedSoftwareDevelopmentCostsMember_2d3ea3d7-d188-46dd-aac5-5fda4207a244" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_MerchantPortfoliosMember_8a1ae952-295b-4a90-9d75-42fd1f3a5ac3" xlink:href="fi-20251231.xsd#fi_MerchantPortfoliosMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_f9294e44-e651-45fd-a3d4-08dc32612558" xlink:to="loc_fi_MerchantPortfoliosMember_8a1ae952-295b-4a90-9d75-42fd1f3a5ac3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_be8ae042-6e9b-4839-ba31-086fa1fcbbdf" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_5cd74d42-4214-42bc-90d6-8a291cbf4950" xlink:to="loc_srt_RangeAxis_be8ae042-6e9b-4839-ba31-086fa1fcbbdf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_be8ae042-6e9b-4839-ba31-086fa1fcbbdf_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_be8ae042-6e9b-4839-ba31-086fa1fcbbdf" xlink:to="loc_srt_RangeMember_be8ae042-6e9b-4839-ba31-086fa1fcbbdf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_81732572-a7df-45cd-8c7c-a0021203610a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_be8ae042-6e9b-4839-ba31-086fa1fcbbdf" xlink:to="loc_srt_RangeMember_81732572-a7df-45cd-8c7c-a0021203610a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_1f5c0c4a-ca60-4a44-bc51-6fdfda71fe56" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_81732572-a7df-45cd-8c7c-a0021203610a" xlink:to="loc_srt_MinimumMember_1f5c0c4a-ca60-4a44-bc51-6fdfda71fe56" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_60c255c8-4424-4f24-9e78-1b5d5911510c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_81732572-a7df-45cd-8c7c-a0021203610a" xlink:to="loc_srt_MaximumMember_60c255c8-4424-4f24-9e78-1b5d5911510c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_fd568c2d-2dda-4d65-8d87-87a7a9e3c122" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_c76061ef-97c3-4a06-9607-17e44166a01a" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_fd568c2d-2dda-4d65-8d87-87a7a9e3c122" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_ProductDevelopmentExpendituresAsPercentageOfRevenue_0ffdf870-5705-48cb-9219-376112cec74c" xlink:href="fi-20251231.xsd#fi_ProductDevelopmentExpendituresAsPercentageOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_c76061ef-97c3-4a06-9607-17e44166a01a" xlink:to="loc_fi_ProductDevelopmentExpendituresAsPercentageOfRevenue_0ffdf870-5705-48cb-9219-376112cec74c" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/SummaryofSignificantAccountingPoliciesEmployeeBenefitPlansDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#SummaryofSignificantAccountingPoliciesEmployeeBenefitPlansDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/SummaryofSignificantAccountingPoliciesEmployeeBenefitPlansDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems_019bb26f-4533-7039-ae62-5d2faee71c79" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansDisclosuresTable_019bb26f-4533-7510-af4f-3c9b01382337" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems_019bb26f-4533-7039-ae62-5d2faee71c79" xlink:to="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansDisclosuresTable_019bb26f-4533-7510-af4f-3c9b01382337" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019bb26f-4533-7c70-aebe-cf1ba152e101" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansDisclosuresTable_019bb26f-4533-7510-af4f-3c9b01382337" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019bb26f-4533-7c70-aebe-cf1ba152e101" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019bb26f-4533-7c70-aebe-cf1ba152e101_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019bb26f-4533-7c70-aebe-cf1ba152e101" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019bb26f-4533-7c70-aebe-cf1ba152e101_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019bb26f-4533-717b-aceb-fadd87b2ab2a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019bb26f-4533-7c70-aebe-cf1ba152e101" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019bb26f-4533-717b-aceb-fadd87b2ab2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019bb26f-a203-7c07-b878-d2ebb277a3ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019bb26f-4533-717b-aceb-fadd87b2ab2a" xlink:to="loc_us-gaap_SubsequentEventMember_019bb26f-a203-7c07-b878-d2ebb277a3ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch_a740583c-1973-4d4c-bf70-d31799d929a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems_019bb26f-4533-7039-ae62-5d2faee71c79" xlink:to="loc_us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch_a740583c-1973-4d4c-bf70-d31799d929a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent_7fd58adf-a536-4e77-afb9-661169c0f828" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems_019bb26f-4533-7039-ae62-5d2faee71c79" xlink:to="loc_us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent_7fd58adf-a536-4e77-afb9-661169c0f828" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_DefinedContributionPlanEmployerMatchingContributionPercentOfAdditionalMatch_9c7d352f-7271-4c64-8cf2-2c0ceb7d6dda" xlink:href="fi-20251231.xsd#fi_DefinedContributionPlanEmployerMatchingContributionPercentOfAdditionalMatch"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems_019bb26f-4533-7039-ae62-5d2faee71c79" xlink:to="loc_fi_DefinedContributionPlanEmployerMatchingContributionPercentOfAdditionalMatch_9c7d352f-7271-4c64-8cf2-2c0ceb7d6dda" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_DefinedContributionPlanMaximumAdditionalAnnualContributionsPerEmployeePercent_32d1a297-b9f9-432f-ad49-9cefc6bbbb45" xlink:href="fi-20251231.xsd#fi_DefinedContributionPlanMaximumAdditionalAnnualContributionsPerEmployeePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems_019bb26f-4533-7039-ae62-5d2faee71c79" xlink:to="loc_fi_DefinedContributionPlanMaximumAdditionalAnnualContributionsPerEmployeePercent_32d1a297-b9f9-432f-ad49-9cefc6bbbb45" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedContributionPlanCostRecognized_bc1d5ed1-362b-44cf-9265-953c8f0110fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedContributionPlanCostRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems_019bb26f-4533-7039-ae62-5d2faee71c79" xlink:to="loc_us-gaap_DefinedContributionPlanCostRecognized_bc1d5ed1-362b-44cf-9265-953c8f0110fc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanActuarialGainLossImmediateRecognitionAsComponentInNetPeriodicBenefitCostCredit_8b27daec-7cef-48ed-b476-a909d6d48c66" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanActuarialGainLossImmediateRecognitionAsComponentInNetPeriodicBenefitCostCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems_019bb26f-4533-7039-ae62-5d2faee71c79" xlink:to="loc_us-gaap_DefinedBenefitPlanActuarialGainLossImmediateRecognitionAsComponentInNetPeriodicBenefitCostCredit_8b27daec-7cef-48ed-b476-a909d6d48c66" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanCostOfProvidingSpecialOrContractualTerminationBenefitRecognizedDuringPeriod_72791154-20ff-4a90-a551-cc6d7c97b0e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanCostOfProvidingSpecialOrContractualTerminationBenefitRecognizedDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems_019bb26f-4533-7039-ae62-5d2faee71c79" xlink:to="loc_us-gaap_DefinedBenefitPlanCostOfProvidingSpecialOrContractualTerminationBenefitRecognizedDuringPeriod_72791154-20ff-4a90-a551-cc6d7c97b0e2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PensionAndOtherPostretirementBenefitsExpenseReversalOfExpenseNoncash_d9db50ec-2d16-4494-bcc6-1adcb3ad00f4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PensionAndOtherPostretirementBenefitsExpenseReversalOfExpenseNoncash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems_019bb26f-4533-7039-ae62-5d2faee71c79" xlink:to="loc_us-gaap_PensionAndOtherPostretirementBenefitsExpenseReversalOfExpenseNoncash_d9db50ec-2d16-4494-bcc6-1adcb3ad00f4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExciseAndSalesTaxes_67409ae0-78a4-4e11-b861-f99667f4424e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ExciseAndSalesTaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems_019bb26f-4533-7039-ae62-5d2faee71c79" xlink:to="loc_us-gaap_ExciseAndSalesTaxes_67409ae0-78a4-4e11-b861-f99667f4424e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostCreditImmediateRecognitionOfActuarialGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleList_019c19c8-33df-7446-b78b-a22f55a707bd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostCreditImmediateRecognitionOfActuarialGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleList"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlansAndOtherPostretirementBenefitPlansTableTextBlockLineItems_019bb26f-4533-7039-ae62-5d2faee71c79" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostCreditImmediateRecognitionOfActuarialGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleList_019c19c8-33df-7446-b78b-a22f55a707bd" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/RevenueRecognitionDisaggregationofRevenueDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#RevenueRecognitionDisaggregationofRevenueDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/RevenueRecognitionDisaggregationofRevenueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_a7787f72-7b8d-4005-a4ef-ed84aeae31c7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_33daa590-16e0-4c47-b6a2-9c407b020906" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_a7787f72-7b8d-4005-a4ef-ed84aeae31c7" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_33daa590-16e0-4c47-b6a2-9c407b020906" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_72a0a58e-27b9-4ffe-afb3-0c5c310bdf8a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_33daa590-16e0-4c47-b6a2-9c407b020906" xlink:to="loc_srt_ProductOrServiceAxis_72a0a58e-27b9-4ffe-afb3-0c5c310bdf8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_72a0a58e-27b9-4ffe-afb3-0c5c310bdf8a_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_72a0a58e-27b9-4ffe-afb3-0c5c310bdf8a" xlink:to="loc_srt_ProductsAndServicesDomain_72a0a58e-27b9-4ffe-afb3-0c5c310bdf8a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_dffcf36e-2580-45c5-bf2e-de0ecd0b1d38" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_72a0a58e-27b9-4ffe-afb3-0c5c310bdf8a" xlink:to="loc_srt_ProductsAndServicesDomain_dffcf36e-2580-45c5-bf2e-de0ecd0b1d38" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_SmallBusinessMember_7b1a9c5b-27e3-4e4f-8b89-aef0835dd73b" xlink:href="fi-20251231.xsd#fi_SmallBusinessMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_dffcf36e-2580-45c5-bf2e-de0ecd0b1d38" xlink:to="loc_fi_SmallBusinessMember_7b1a9c5b-27e3-4e4f-8b89-aef0835dd73b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_EnterpriseMember_b14fd3d7-a0ea-4725-b905-b656fa4fc3da" xlink:href="fi-20251231.xsd#fi_EnterpriseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_dffcf36e-2580-45c5-bf2e-de0ecd0b1d38" xlink:to="loc_fi_EnterpriseMember_b14fd3d7-a0ea-4725-b905-b656fa4fc3da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_ProcessingMember_20983b1e-7400-4477-ad8d-b243c5972c62" xlink:href="fi-20251231.xsd#fi_ProcessingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_dffcf36e-2580-45c5-bf2e-de0ecd0b1d38" xlink:to="loc_fi_ProcessingMember_20983b1e-7400-4477-ad8d-b243c5972c62" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_DigitalPaymentsMember_8353dc7e-9352-4bf7-a576-00cf924fe4d8" xlink:href="fi-20251231.xsd#fi_DigitalPaymentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_dffcf36e-2580-45c5-bf2e-de0ecd0b1d38" xlink:to="loc_fi_DigitalPaymentsMember_8353dc7e-9352-4bf7-a576-00cf924fe4d8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_IssuingMember_f521bdfd-152c-4f8c-852f-0da3af5757ba" xlink:href="fi-20251231.xsd#fi_IssuingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_dffcf36e-2580-45c5-bf2e-de0ecd0b1d38" xlink:to="loc_fi_IssuingMember_f521bdfd-152c-4f8c-852f-0da3af5757ba" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BankingMember_68f2072a-2555-4ba4-91c4-c092cf5e4aa1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BankingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_dffcf36e-2580-45c5-bf2e-de0ecd0b1d38" xlink:to="loc_us-gaap_BankingMember_68f2072a-2555-4ba4-91c4-c092cf5e4aa1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_9302d647-32b7-477f-b2ec-211c82987a08" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_33daa590-16e0-4c47-b6a2-9c407b020906" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_9302d647-32b7-477f-b2ec-211c82987a08" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_9302d647-32b7-477f-b2ec-211c82987a08_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_9302d647-32b7-477f-b2ec-211c82987a08" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_9302d647-32b7-477f-b2ec-211c82987a08_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_54b5511a-169f-4be3-b8e0-f0ac092aa719" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_9302d647-32b7-477f-b2ec-211c82987a08" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_54b5511a-169f-4be3-b8e0-f0ac092aa719" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeographicConcentrationRiskMember_0e07a8b0-2a4d-4685-89be-6788672421a8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeographicConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_54b5511a-169f-4be3-b8e0-f0ac092aa719" xlink:to="loc_us-gaap_GeographicConcentrationRiskMember_0e07a8b0-2a4d-4685-89be-6788672421a8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_a98cc739-6875-497d-b20a-c21c641a4f33" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_33daa590-16e0-4c47-b6a2-9c407b020906" xlink:to="loc_srt_StatementGeographicalAxis_a98cc739-6875-497d-b20a-c21c641a4f33" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_a98cc739-6875-497d-b20a-c21c641a4f33_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_a98cc739-6875-497d-b20a-c21c641a4f33" xlink:to="loc_srt_SegmentGeographicalDomain_a98cc739-6875-497d-b20a-c21c641a4f33_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_3c3a35e6-ac8d-4e7b-af79-5d1cbdc3e1f0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_a98cc739-6875-497d-b20a-c21c641a4f33" xlink:to="loc_srt_SegmentGeographicalDomain_3c3a35e6-ac8d-4e7b-af79-5d1cbdc3e1f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_6eb62b89-3726-4df2-b357-b18f3cda732a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_3c3a35e6-ac8d-4e7b-af79-5d1cbdc3e1f0" xlink:to="loc_us-gaap_NonUsMember_6eb62b89-3726-4df2-b357-b18f3cda732a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_1c7bb963-7a6a-4ec9-930f-48053e548dbc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_33daa590-16e0-4c47-b6a2-9c407b020906" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_1c7bb963-7a6a-4ec9-930f-48053e548dbc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1c7bb963-7a6a-4ec9-930f-48053e548dbc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_1c7bb963-7a6a-4ec9-930f-48053e548dbc" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1c7bb963-7a6a-4ec9-930f-48053e548dbc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_7f681d4e-9641-447c-b608-d1d0a1469e5a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_1c7bb963-7a6a-4ec9-930f-48053e548dbc" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_7f681d4e-9641-447c-b608-d1d0a1469e5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerMember_a1541b38-f1c9-4c29-b27e-f200dc69c036" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_7f681d4e-9641-447c-b608-d1d0a1469e5a" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerMember_a1541b38-f1c9-4c29-b27e-f200dc69c036" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_60837de3-64f0-420b-9f7a-65e2589bec99" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_33daa590-16e0-4c47-b6a2-9c407b020906" xlink:to="loc_srt_ConsolidationItemsAxis_60837de3-64f0-420b-9f7a-65e2589bec99" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_60837de3-64f0-420b-9f7a-65e2589bec99_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_60837de3-64f0-420b-9f7a-65e2589bec99" xlink:to="loc_srt_ConsolidationItemsDomain_60837de3-64f0-420b-9f7a-65e2589bec99_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_6da01c7f-cae0-4af3-8cfc-9f21244d5c44" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_60837de3-64f0-420b-9f7a-65e2589bec99" xlink:to="loc_srt_ConsolidationItemsDomain_6da01c7f-cae0-4af3-8cfc-9f21244d5c44" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_ff66098a-142a-4c7e-94cc-cf9db2da4a23" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_6da01c7f-cae0-4af3-8cfc-9f21244d5c44" xlink:to="loc_us-gaap_OperatingSegmentsMember_ff66098a-142a-4c7e-94cc-cf9db2da4a23" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_CorporateReconcilingItemsAndEliminationsMember_70771463-145d-4cf1-9ab1-a0bff81fffa2" xlink:href="fi-20251231.xsd#fi_CorporateReconcilingItemsAndEliminationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_6da01c7f-cae0-4af3-8cfc-9f21244d5c44" xlink:to="loc_fi_CorporateReconcilingItemsAndEliminationsMember_70771463-145d-4cf1-9ab1-a0bff81fffa2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_a9d3b472-9cc8-4cdb-990b-d9170e827a5b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_33daa590-16e0-4c47-b6a2-9c407b020906" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_a9d3b472-9cc8-4cdb-990b-d9170e827a5b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_a9d3b472-9cc8-4cdb-990b-d9170e827a5b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_a9d3b472-9cc8-4cdb-990b-d9170e827a5b" xlink:to="loc_us-gaap_SegmentDomain_a9d3b472-9cc8-4cdb-990b-d9170e827a5b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_59ffe944-0240-4236-a181-71757242ee10" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_a9d3b472-9cc8-4cdb-990b-d9170e827a5b" xlink:to="loc_us-gaap_SegmentDomain_59ffe944-0240-4236-a181-71757242ee10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_MerchantSolutionsSegmentMember_3b4d2436-969e-44e9-8a60-179edcc8c812" xlink:href="fi-20251231.xsd#fi_MerchantSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_59ffe944-0240-4236-a181-71757242ee10" xlink:to="loc_fi_MerchantSolutionsSegmentMember_3b4d2436-969e-44e9-8a60-179edcc8c812" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_FinancialSolutionsSegmentMember_32a0eda4-24fa-4376-85c2-bd153e401c96" xlink:href="fi-20251231.xsd#fi_FinancialSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_59ffe944-0240-4236-a181-71757242ee10" xlink:to="loc_fi_FinancialSolutionsSegmentMember_32a0eda4-24fa-4376-85c2-bd153e401c96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_0cf849a6-eca5-4892-adee-511539f03956" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_a7787f72-7b8d-4005-a4ef-ed84aeae31c7" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_0cf849a6-eca5-4892-adee-511539f03956" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_ce76c8d2-c435-4fc7-bebd-711d736ca71e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_a7787f72-7b8d-4005-a4ef-ed84aeae31c7" xlink:to="loc_us-gaap_Revenues_ce76c8d2-c435-4fc7-bebd-711d736ca71e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueNotFromContractWithCustomer_019b0dd6-1caf-7f2b-89b6-7cbe71cc4102" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueNotFromContractWithCustomer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_a7787f72-7b8d-4005-a4ef-ed84aeae31c7" xlink:to="loc_us-gaap_RevenueNotFromContractWithCustomer_019b0dd6-1caf-7f2b-89b6-7cbe71cc4102" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/RevenueRecognitionRemainingPerformanceObligationDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#RevenueRecognitionRemainingPerformanceObligationDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/RevenueRecognitionRemainingPerformanceObligationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_3a4e4abb-45a9-4650-93a5-d75645198f92" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1a0b5696-15cb-4f3e-991b-45a13ea46944" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_3a4e4abb-45a9-4650-93a5-d75645198f92" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1a0b5696-15cb-4f3e-991b-45a13ea46944" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_c6c6b900-f127-4aa4-aaad-87bc3edd6813" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1a0b5696-15cb-4f3e-991b-45a13ea46944" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_c6c6b900-f127-4aa4-aaad-87bc3edd6813" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_58e196c2-a03b-4dc9-b551-a7aeb3d50d02" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_3a4e4abb-45a9-4650-93a5-d75645198f92" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_58e196c2-a03b-4dc9-b551-a7aeb3d50d02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_b54f6085-4290-4c5c-ac4e-e961ffb7c65f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_3a4e4abb-45a9-4650-93a5-d75645198f92" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_b54f6085-4290-4c5c-ac4e-e961ffb7c65f" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/RevenueRecognitionRemainingPerformanceObligationDetails_1" xlink:type="simple" xlink:href="fi-20251231.xsd#RevenueRecognitionRemainingPerformanceObligationDetails_1"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/RevenueRecognitionRemainingPerformanceObligationDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_3a4e4abb-45a9-4650-93a5-d75645198f92" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1a0b5696-15cb-4f3e-991b-45a13ea46944" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_3a4e4abb-45a9-4650-93a5-d75645198f92" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_1a0b5696-15cb-4f3e-991b-45a13ea46944" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_58e196c2-a03b-4dc9-b551-a7aeb3d50d02" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_3a4e4abb-45a9-4650-93a5-d75645198f92" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_58e196c2-a03b-4dc9-b551-a7aeb3d50d02" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_b54f6085-4290-4c5c-ac4e-e961ffb7c65f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_3a4e4abb-45a9-4650-93a5-d75645198f92" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_b54f6085-4290-4c5c-ac4e-e961ffb7c65f" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/RevenueRecognitionCapitalizedSalesCommissionsandConversionorImplementationCostsDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#RevenueRecognitionCapitalizedSalesCommissionsandConversionorImplementationCostsDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/RevenueRecognitionCapitalizedSalesCommissionsandConversionorImplementationCostsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostLineItems_e1ba61cc-1cf0-4a50-90fe-8e4c667b38a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalizedContractCostLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostTable_c6f5bbb1-2783-44a6-8bc8-949f2b38afde" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalizedContractCostTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_e1ba61cc-1cf0-4a50-90fe-8e4c667b38a4" xlink:to="loc_us-gaap_CapitalizedContractCostTable_c6f5bbb1-2783-44a6-8bc8-949f2b38afde" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostAxis_7fb2fac7-01de-460b-8600-d41c602863d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalizedContractCostAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_CapitalizedContractCostTable_c6f5bbb1-2783-44a6-8bc8-949f2b38afde" xlink:to="loc_us-gaap_CapitalizedContractCostAxis_7fb2fac7-01de-460b-8600-d41c602863d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostDomain_7fb2fac7-01de-460b-8600-d41c602863d9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalizedContractCostDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CapitalizedContractCostAxis_7fb2fac7-01de-460b-8600-d41c602863d9" xlink:to="loc_us-gaap_CapitalizedContractCostDomain_7fb2fac7-01de-460b-8600-d41c602863d9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostDomain_81d8535b-be51-482e-9c92-df9a08823635" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalizedContractCostDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CapitalizedContractCostAxis_7fb2fac7-01de-460b-8600-d41c602863d9" xlink:to="loc_us-gaap_CapitalizedContractCostDomain_81d8535b-be51-482e-9c92-df9a08823635" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_SalesCommissionsMember_47abbc07-0715-43e7-b090-09ab1465f5e8" xlink:href="fi-20251231.xsd#fi_SalesCommissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostDomain_81d8535b-be51-482e-9c92-df9a08823635" xlink:to="loc_fi_SalesCommissionsMember_47abbc07-0715-43e7-b090-09ab1465f5e8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_ConversionOrImplementationCostsMember_2db66256-6dfa-4a86-a183-71a31052c0ec" xlink:href="fi-20251231.xsd#fi_ConversionOrImplementationCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostDomain_81d8535b-be51-482e-9c92-df9a08823635" xlink:to="loc_fi_ConversionOrImplementationCostsMember_2db66256-6dfa-4a86-a183-71a31052c0ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedContractCostGross_fd9904a4-86d5-407b-ab2b-7878eccd2faf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalizedContractCostGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizedContractCostLineItems_e1ba61cc-1cf0-4a50-90fe-8e4c667b38a4" xlink:to="loc_us-gaap_CapitalizedContractCostGross_fd9904a4-86d5-407b-ab2b-7878eccd2faf" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/AcquisitionsDispositionsandOtherTransactionsNarrativeDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#AcquisitionsDispositionsandOtherTransactionsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/AcquisitionsDispositionsandOtherTransactionsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5d201bcd-fdd2-4554-b5c0-377e9d9ba775" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5d201bcd-fdd2-4554-b5c0-377e9d9ba775" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_b2c59035-4c74-4635-80ff-1f33ceaeda2f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5d201bcd-fdd2-4554-b5c0-377e9d9ba775" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_b2c59035-4c74-4635-80ff-1f33ceaeda2f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_b2c59035-4c74-4635-80ff-1f33ceaeda2f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_b2c59035-4c74-4635-80ff-1f33ceaeda2f" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_b2c59035-4c74-4635-80ff-1f33ceaeda2f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_12cf14b5-2693-47eb-9924-0e79018aa88f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_b2c59035-4c74-4635-80ff-1f33ceaeda2f" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_12cf14b5-2693-47eb-9924-0e79018aa88f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_StoneCastleMember_019b3894-94d1-7a86-aba9-bd64babde41e" xlink:href="fi-20251231.xsd#fi_StoneCastleMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_12cf14b5-2693-47eb-9924-0e79018aa88f" xlink:to="loc_fi_StoneCastleMember_019b3894-94d1-7a86-aba9-bd64babde41e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_CCVGroupB.V.Member_830c42f3-9745-4748-9dd8-fbb95b266223" xlink:href="fi-20251231.xsd#fi_CCVGroupB.V.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_12cf14b5-2693-47eb-9924-0e79018aa88f" xlink:to="loc_fi_CCVGroupB.V.Member_830c42f3-9745-4748-9dd8-fbb95b266223" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_PayfareMember_6902c0ac-9056-4d1a-bcd8-7a6dbd4b4864" xlink:href="fi-20251231.xsd#fi_PayfareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_12cf14b5-2693-47eb-9924-0e79018aa88f" xlink:to="loc_fi_PayfareMember_6902c0ac-9056-4d1a-bcd8-7a6dbd4b4864" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_PinchPaymentsMoneyMoneyCardFreeSCGAndTDMerchantCanadaMember_62f89a7d-9c63-4c40-832d-2461162e7bc5" xlink:href="fi-20251231.xsd#fi_PinchPaymentsMoneyMoneyCardFreeSCGAndTDMerchantCanadaMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_12cf14b5-2693-47eb-9924-0e79018aa88f" xlink:to="loc_fi_PinchPaymentsMoneyMoneyCardFreeSCGAndTDMerchantCanadaMember_62f89a7d-9c63-4c40-832d-2461162e7bc5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_SkytefAndSledMember_ca338477-6e6f-41b9-ba77-47e8aedd873c" xlink:href="fi-20251231.xsd#fi_SkytefAndSledMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_12cf14b5-2693-47eb-9924-0e79018aa88f" xlink:to="loc_fi_SkytefAndSledMember_ca338477-6e6f-41b9-ba77-47e8aedd873c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_ICICIMerchantServicesPrivateLimitedMember_1c8ab8e0-68e0-4768-92a2-cb3ea14cd7b0" xlink:href="fi-20251231.xsd#fi_ICICIMerchantServicesPrivateLimitedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_12cf14b5-2693-47eb-9924-0e79018aa88f" xlink:to="loc_fi_ICICIMerchantServicesPrivateLimitedMember_1c8ab8e0-68e0-4768-92a2-cb3ea14cd7b0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_AIBMSMember_783a8dd2-7053-4d98-bd1f-bc9a69cd1268" xlink:href="fi-20251231.xsd#fi_AIBMSMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_12cf14b5-2693-47eb-9924-0e79018aa88f" xlink:to="loc_fi_AIBMSMember_783a8dd2-7053-4d98-bd1f-bc9a69cd1268" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_8964b53d-387c-4f63-8710-9b6aef82dcda" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5d201bcd-fdd2-4554-b5c0-377e9d9ba775" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_8964b53d-387c-4f63-8710-9b6aef82dcda" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_8964b53d-387c-4f63-8710-9b6aef82dcda_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_8964b53d-387c-4f63-8710-9b6aef82dcda" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_8964b53d-387c-4f63-8710-9b6aef82dcda_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_6c1c0000-d15a-48c7-b219-99323c80037f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_8964b53d-387c-4f63-8710-9b6aef82dcda" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_6c1c0000-d15a-48c7-b219-99323c80037f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember_9a137f8e-1b43-4b08-8f16-660c31a5d702" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_6c1c0000-d15a-48c7-b219-99323c80037f" xlink:to="loc_us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember_9a137f8e-1b43-4b08-8f16-660c31a5d702" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_93e955f5-e38b-48e9-a315-32f43420e3ca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5d201bcd-fdd2-4554-b5c0-377e9d9ba775" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_93e955f5-e38b-48e9-a315-32f43420e3ca" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_93e955f5-e38b-48e9-a315-32f43420e3ca_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_93e955f5-e38b-48e9-a315-32f43420e3ca" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_93e955f5-e38b-48e9-a315-32f43420e3ca_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_046adeaf-ea79-4e67-83b3-a1db0e49a568" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_93e955f5-e38b-48e9-a315-32f43420e3ca" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_046adeaf-ea79-4e67-83b3-a1db0e49a568" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_FinancialReconciliationBusinessMember_8e0a8e6a-b93d-4a39-aba8-ccd3ac11a902" xlink:href="fi-20251231.xsd#fi_FinancialReconciliationBusinessMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_046adeaf-ea79-4e67-83b3-a1db0e49a568" xlink:to="loc_fi_FinancialReconciliationBusinessMember_8e0a8e6a-b93d-4a39-aba8-ccd3ac11a902" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019b0de7-f074-7a00-bcd6-fcb0b2ec7f14" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5d201bcd-fdd2-4554-b5c0-377e9d9ba775" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019b0de7-f074-7a00-bcd6-fcb0b2ec7f14" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019b0de7-f074-7a00-bcd6-fcb0b2ec7f14_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019b0de7-f074-7a00-bcd6-fcb0b2ec7f14" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019b0de7-f074-7a00-bcd6-fcb0b2ec7f14_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019b0de7-f074-711d-baab-35c7fa0e07da" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019b0de7-f074-7a00-bcd6-fcb0b2ec7f14" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019b0de7-f074-711d-baab-35c7fa0e07da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_019be69e-3873-7407-874a-01cace0eddee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerRelatedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019b0de7-f074-711d-baab-35c7fa0e07da" xlink:to="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_019be69e-3873-7407-874a-01cace0eddee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_AcquiredSoftwareAndTechnologyMember_019b3898-4acd-7252-942c-323686bc59ef" xlink:href="fi-20251231.xsd#fi_AcquiredSoftwareAndTechnologyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019b0de7-f074-711d-baab-35c7fa0e07da" xlink:to="loc_fi_AcquiredSoftwareAndTechnologyMember_019b3898-4acd-7252-942c-323686bc59ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksMember_019be69d-4c7a-7834-a842-74d1c67cd1b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TrademarksMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019b0de7-f074-711d-baab-35c7fa0e07da" xlink:to="loc_us-gaap_TrademarksMember_019be69d-4c7a-7834-a842-74d1c67cd1b0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_019c19c3-183f-7f97-a3f0-68a38688bf5e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComputerSoftwareIntangibleAssetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019b0de7-f074-711d-baab-35c7fa0e07da" xlink:to="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_019c19c3-183f-7f97-a3f0-68a38688bf5e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_d37c2e4b-61e6-4a32-9ae4-9c304e2ceab1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_d37c2e4b-61e6-4a32-9ae4-9c304e2ceab1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAcquiredFromAcquisition_b57b08b1-27e8-486c-8d50-40ddc2f84241" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAcquiredFromAcquisition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_CashAcquiredFromAcquisition_b57b08b1-27e8-486c-8d50-40ddc2f84241" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_4b6a9453-bd72-4682-a638-ef978f566f58" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_4b6a9453-bd72-4682-a638-ef978f566f58" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_e48abcff-9b24-4f9c-875f-ca6a8f52817a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_e48abcff-9b24-4f9c-875f-ca6a8f52817a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_9b6146e6-a4d5-4755-91e9-ed8de6394baa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_Goodwill_9b6146e6-a4d5-4755-91e9-ed8de6394baa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_d6c00b23-3637-48a8-ab98-c2c164d45f04" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_d6c00b23-3637-48a8-ab98-c2c164d45f04" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_abe77cd5-cd07-44db-8d82-04eec541c7bd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_abe77cd5-cd07-44db-8d82-04eec541c7bd" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_90ad72d8-eff7-4fd1-8e51-14a4aca44017" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_90ad72d8-eff7-4fd1-8e51-14a4aca44017" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_6983cfd2-5c44-4998-9097-2844de290f8b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_6983cfd2-5c44-4998-9097-2844de290f8b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_aa3c47ac-4aba-409e-bd69-65b186422113" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromDivestitureOfBusinesses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_aa3c47ac-4aba-409e-bd69-65b186422113" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfBusiness_96bebdc4-9379-425e-b80e-c5e1c00708f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GainLossOnSaleOfBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_GainLossOnSaleOfBusiness_96bebdc4-9379-425e-b80e-c5e1c00708f7" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_cb5c0063-e395-4126-916d-21402613b737" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_cb5c0063-e395-4126-916d-21402613b737" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationGoodwill1_91836736-4a86-45ce-917a-d29fba06063b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationGoodwill1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationGoodwill1_91836736-4a86-45ce-917a-d29fba06063b" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_DisposalGroupIncludingDiscontinuedOperationTradeReceivableAndCapitalizedSoftware_0cc364de-a7ab-418c-9c70-6373935d1d75" xlink:href="fi-20251231.xsd#fi_DisposalGroupIncludingDiscontinuedOperationTradeReceivableAndCapitalizedSoftware"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_fi_DisposalGroupIncludingDiscontinuedOperationTradeReceivableAndCapitalizedSoftware_0cc364de-a7ab-418c-9c70-6373935d1d75" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_DisposalGroupIncludingDiscontinuedOperationAccumulatedForeignCurrencyTranslationLoss_51306a3d-c64e-4715-ab04-f4a2abc58f14" xlink:href="fi-20251231.xsd#fi_DisposalGroupIncludingDiscontinuedOperationAccumulatedForeignCurrencyTranslationLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_fi_DisposalGroupIncludingDiscontinuedOperationAccumulatedForeignCurrencyTranslationLoss_51306a3d-c64e-4715-ab04-f4a2abc58f14" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_1f1fbdd2-eff8-4c71-bda9-a38e43a607a3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_4456ebc7-757c-435a-90fa-b6102ab27ff0" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_1f1fbdd2-eff8-4c71-bda9-a38e43a607a3" xlink:type="arc" order="15"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/IntangibleAssetsScheduleofIntangibleAssetsbyClassDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#IntangibleAssetsScheduleofIntangibleAssetsbyClassDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/IntangibleAssetsScheduleofIntangibleAssetsbyClassDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_514622d8-cfd6-4ef3-826d-946be78b7109" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_c867bffe-4e57-4069-bc3e-8f295a22ffea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_514622d8-cfd6-4ef3-826d-946be78b7109" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_c867bffe-4e57-4069-bc3e-8f295a22ffea" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_a0dfdd35-be4d-4cf1-93d4-d756ea7824db" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_c867bffe-4e57-4069-bc3e-8f295a22ffea" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_a0dfdd35-be4d-4cf1-93d4-d756ea7824db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_a0dfdd35-be4d-4cf1-93d4-d756ea7824db_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_a0dfdd35-be4d-4cf1-93d4-d756ea7824db" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_a0dfdd35-be4d-4cf1-93d4-d756ea7824db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b8fad191-f9b7-4294-948a-c4822c83293d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_a0dfdd35-be4d-4cf1-93d4-d756ea7824db" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b8fad191-f9b7-4294-948a-c4822c83293d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_cae39022-f3b2-4708-9a2d-356cb27c1025" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerRelatedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b8fad191-f9b7-4294-948a-c4822c83293d" xlink:to="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_cae39022-f3b2-4708-9a2d-356cb27c1025" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_AcquiredSoftwareAndTechnologyMember_f354644a-9687-471c-8505-ee96e1d7fbcf" xlink:href="fi-20251231.xsd#fi_AcquiredSoftwareAndTechnologyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b8fad191-f9b7-4294-948a-c4822c83293d" xlink:to="loc_fi_AcquiredSoftwareAndTechnologyMember_f354644a-9687-471c-8505-ee96e1d7fbcf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_fd998dcf-47a7-49ea-b559-094b7c7a67c2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b8fad191-f9b7-4294-948a-c4822c83293d" xlink:to="loc_us-gaap_TradeNamesMember_fd998dcf-47a7-49ea-b559-094b7c7a67c2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_e428e67f-c5a8-4470-955e-0d1af7cd07aa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ComputerSoftwareIntangibleAssetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b8fad191-f9b7-4294-948a-c4822c83293d" xlink:to="loc_us-gaap_ComputerSoftwareIntangibleAssetMember_e428e67f-c5a8-4470-955e-0d1af7cd07aa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_CapitalizedSoftwareDevelopmentCostsMember_fefd177c-88a5-4554-a017-45a74e8f9a1d" xlink:href="fi-20251231.xsd#fi_CapitalizedSoftwareDevelopmentCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b8fad191-f9b7-4294-948a-c4822c83293d" xlink:to="loc_fi_CapitalizedSoftwareDevelopmentCostsMember_fefd177c-88a5-4554-a017-45a74e8f9a1d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_6c23a1ff-5596-44fd-9c7c-011824bb36f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_514622d8-cfd6-4ef3-826d-946be78b7109" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_6c23a1ff-5596-44fd-9c7c-011824bb36f5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_64b8cfd2-19c2-40cd-a99e-b5efc371ab1c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_514622d8-cfd6-4ef3-826d-946be78b7109" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_64b8cfd2-19c2-40cd-a99e-b5efc371ab1c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_ef908b36-48f1-419f-bb63-db83280fd20f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_514622d8-cfd6-4ef3-826d-946be78b7109" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_ef908b36-48f1-419f-bb63-db83280fd20f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/IntangibleAssetsNarrativeDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#IntangibleAssetsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/IntangibleAssetsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_ac8febe1-f14f-4e5a-b614-2c01b62eb70e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_1b146e56-d1e7-4bc1-9be1-e14885df1f2d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_ac8febe1-f14f-4e5a-b614-2c01b62eb70e" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_1b146e56-d1e7-4bc1-9be1-e14885df1f2d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_d354e0ba-10df-4658-b573-1bd2be649454" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_1b146e56-d1e7-4bc1-9be1-e14885df1f2d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_d354e0ba-10df-4658-b573-1bd2be649454" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d354e0ba-10df-4658-b573-1bd2be649454_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_d354e0ba-10df-4658-b573-1bd2be649454" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d354e0ba-10df-4658-b573-1bd2be649454_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_6c3906ad-ae7f-4bfd-95f1-eca1ca434c68" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_d354e0ba-10df-4658-b573-1bd2be649454" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_6c3906ad-ae7f-4bfd-95f1-eca1ca434c68" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_CapitalizedSoftwareDevelopmentCostsMember_43a6e189-bb4f-4144-91d6-48139ea5bd5d" xlink:href="fi-20251231.xsd#fi_CapitalizedSoftwareDevelopmentCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_6c3906ad-ae7f-4bfd-95f1-eca1ca434c68" xlink:to="loc_fi_CapitalizedSoftwareDevelopmentCostsMember_43a6e189-bb4f-4144-91d6-48139ea5bd5d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizedComputerSoftwareAdditions_67762817-7249-4bc3-9157-2f30a42561cd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CapitalizedComputerSoftwareAdditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_ac8febe1-f14f-4e5a-b614-2c01b62eb70e" xlink:to="loc_us-gaap_CapitalizedComputerSoftwareAdditions_67762817-7249-4bc3-9157-2f30a42561cd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_19c35b81-e875-472d-b9ce-28b46ae3e59e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_ac8febe1-f14f-4e5a-b614-2c01b62eb70e" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_19c35b81-e875-472d-b9ce-28b46ae3e59e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/GoodwillDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#GoodwillDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/GoodwillDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_0d89b4bb-d639-4785-a74f-b74404f0e7e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_b3e43d8b-3651-43c5-a6d2-08ecdd3acf37" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_0d89b4bb-d639-4785-a74f-b74404f0e7e5" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_b3e43d8b-3651-43c5-a6d2-08ecdd3acf37" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_f07db663-80ec-46f7-bb18-1778d64ee449" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_b3e43d8b-3651-43c5-a6d2-08ecdd3acf37" xlink:to="loc_srt_ConsolidationItemsAxis_f07db663-80ec-46f7-bb18-1778d64ee449" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_f07db663-80ec-46f7-bb18-1778d64ee449_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_f07db663-80ec-46f7-bb18-1778d64ee449" xlink:to="loc_srt_ConsolidationItemsDomain_f07db663-80ec-46f7-bb18-1778d64ee449_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_fc82fa92-92c4-499b-827c-d8a68e61b1f0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_f07db663-80ec-46f7-bb18-1778d64ee449" xlink:to="loc_srt_ConsolidationItemsDomain_fc82fa92-92c4-499b-827c-d8a68e61b1f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_f1fac196-7e47-47e0-9232-af0545234254" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_fc82fa92-92c4-499b-827c-d8a68e61b1f0" xlink:to="loc_us-gaap_OperatingSegmentsMember_f1fac196-7e47-47e0-9232-af0545234254" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_eccc1907-5edd-4e8f-9009-4cc32db5e73d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_b3e43d8b-3651-43c5-a6d2-08ecdd3acf37" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_eccc1907-5edd-4e8f-9009-4cc32db5e73d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_eccc1907-5edd-4e8f-9009-4cc32db5e73d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_eccc1907-5edd-4e8f-9009-4cc32db5e73d" xlink:to="loc_us-gaap_SegmentDomain_eccc1907-5edd-4e8f-9009-4cc32db5e73d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_366315c4-d90b-4149-bf70-22ae15552c6f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_eccc1907-5edd-4e8f-9009-4cc32db5e73d" xlink:to="loc_us-gaap_SegmentDomain_366315c4-d90b-4149-bf70-22ae15552c6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_AcceptanceSegmentMember_72c7605e-9f4a-4760-a5f6-3ce475841ae7" xlink:href="fi-20251231.xsd#fi_AcceptanceSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_366315c4-d90b-4149-bf70-22ae15552c6f" xlink:to="loc_fi_AcceptanceSegmentMember_72c7605e-9f4a-4760-a5f6-3ce475841ae7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_FintechSegmentMember_620e8217-90d6-4406-b218-8712326361f0" xlink:href="fi-20251231.xsd#fi_FintechSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_366315c4-d90b-4149-bf70-22ae15552c6f" xlink:to="loc_fi_FintechSegmentMember_620e8217-90d6-4406-b218-8712326361f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_PaymentsSegmentMember_0172c8f9-2a4f-4652-8d9f-06ffdfedca86" xlink:href="fi-20251231.xsd#fi_PaymentsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_366315c4-d90b-4149-bf70-22ae15552c6f" xlink:to="loc_fi_PaymentsSegmentMember_0172c8f9-2a4f-4652-8d9f-06ffdfedca86" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_MerchantSolutionsSegmentMember_1c21c072-9ab6-4919-a6e5-78d1e946f84f" xlink:href="fi-20251231.xsd#fi_MerchantSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_366315c4-d90b-4149-bf70-22ae15552c6f" xlink:to="loc_fi_MerchantSolutionsSegmentMember_1c21c072-9ab6-4919-a6e5-78d1e946f84f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_FinancialSolutionsSegmentMember_7cba070c-3d5c-4323-9778-15f374d43a69" xlink:href="fi-20251231.xsd#fi_FinancialSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_366315c4-d90b-4149-bf70-22ae15552c6f" xlink:to="loc_fi_FinancialSolutionsSegmentMember_7cba070c-3d5c-4323-9778-15f374d43a69" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillRollForward_504a3103-b92c-44a3-abc2-ba98193a6783" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_0d89b4bb-d639-4785-a74f-b74404f0e7e5" xlink:to="loc_us-gaap_GoodwillRollForward_504a3103-b92c-44a3-abc2-ba98193a6783" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_6a2e3e3f-91c8-4cfc-826d-ffd1f7b1039e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_504a3103-b92c-44a3-abc2-ba98193a6783" xlink:to="loc_us-gaap_Goodwill_6a2e3e3f-91c8-4cfc-826d-ffd1f7b1039e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillTransfers_c2673c24-d0a6-48a0-8be1-d7ddd1ddcfcd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillTransfers"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_504a3103-b92c-44a3-abc2-ba98193a6783" xlink:to="loc_us-gaap_GoodwillTransfers_c2673c24-d0a6-48a0-8be1-d7ddd1ddcfcd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAcquiredDuringPeriod_019c28fa-1fbf-7267-9c23-e1a14c20b814" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillAcquiredDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_504a3103-b92c-44a3-abc2-ba98193a6783" xlink:to="loc_us-gaap_GoodwillAcquiredDuringPeriod_019c28fa-1fbf-7267-9c23-e1a14c20b814" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_3977a098-f869-445f-a05d-27e04eaade3c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GoodwillForeignCurrencyTranslationGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_504a3103-b92c-44a3-abc2-ba98193a6783" xlink:to="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_3977a098-f869-445f-a05d-27e04eaade3c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_329a6818-dbcb-4cbc-8631-2edfc8732fa0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Goodwill"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/InvestmentsinUnconsolidatedAffiliatesDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#InvestmentsinUnconsolidatedAffiliatesDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/InvestmentsinUnconsolidatedAffiliatesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_32370ccb-93f6-4432-b7b9-6dbee3aaeafc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_32370ccb-93f6-4432-b7b9-6dbee3aaeafc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_6cef1003-34be-41f7-b7e9-eae6c21e015e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_32370ccb-93f6-4432-b7b9-6dbee3aaeafc" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_6cef1003-34be-41f7-b7e9-eae6c21e015e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_6cef1003-34be-41f7-b7e9-eae6c21e015e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_6cef1003-34be-41f7-b7e9-eae6c21e015e" xlink:to="loc_us-gaap_RelatedPartyDomain_6cef1003-34be-41f7-b7e9-eae6c21e015e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_697ddb92-c75e-4677-90eb-86494cc935eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_6cef1003-34be-41f7-b7e9-eae6c21e015e" xlink:to="loc_us-gaap_RelatedPartyDomain_697ddb92-c75e-4677-90eb-86494cc935eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_BancofAmericaMerchantServicesMember_d3ab24d1-2a12-4aef-80db-46c6c44d55a8" xlink:href="fi-20251231.xsd#fi_BancofAmericaMerchantServicesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_697ddb92-c75e-4677-90eb-86494cc935eb" xlink:to="loc_fi_BancofAmericaMerchantServicesMember_d3ab24d1-2a12-4aef-80db-46c6c44d55a8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_3aab4e52-afce-4c10-b9a4-4b5db87a844b" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_32370ccb-93f6-4432-b7b9-6dbee3aaeafc" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_3aab4e52-afce-4c10-b9a4-4b5db87a844b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_3aab4e52-afce-4c10-b9a4-4b5db87a844b_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_3aab4e52-afce-4c10-b9a4-4b5db87a844b" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_3aab4e52-afce-4c10-b9a4-4b5db87a844b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_d913b722-8919-4b86-b2ba-8b4b7ce97bd1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_3aab4e52-afce-4c10-b9a4-4b5db87a844b" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_d913b722-8919-4b86-b2ba-8b4b7ce97bd1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_WellsFargoMerchantServicesWFMSMember_5df0d63d-aa05-4fe0-9efe-bfba786a6574" xlink:href="fi-20251231.xsd#fi_WellsFargoMerchantServicesWFMSMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_d913b722-8919-4b86-b2ba-8b4b7ce97bd1" xlink:to="loc_fi_WellsFargoMerchantServicesWFMSMember_5df0d63d-aa05-4fe0-9efe-bfba786a6574" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_LendingJointVenturesMember_f66b311a-ed5c-4c54-9c7d-3618b2f44e67" xlink:href="fi-20251231.xsd#fi_LendingJointVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_d913b722-8919-4b86-b2ba-8b4b7ce97bd1" xlink:to="loc_fi_LendingJointVenturesMember_f66b311a-ed5c-4c54-9c7d-3618b2f44e67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_OtherStrategicInvestmentsMember_5e4e7c91-5c4a-48b8-9cd1-4a685c1957b8" xlink:href="fi-20251231.xsd#fi_OtherStrategicInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_d913b722-8919-4b86-b2ba-8b4b7ce97bd1" xlink:to="loc_fi_OtherStrategicInvestmentsMember_5e4e7c91-5c4a-48b8-9cd1-4a685c1957b8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_92ed1a98-c849-413c-a2d3-307c36d7b48b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_32370ccb-93f6-4432-b7b9-6dbee3aaeafc" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_92ed1a98-c849-413c-a2d3-307c36d7b48b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_92ed1a98-c849-413c-a2d3-307c36d7b48b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_92ed1a98-c849-413c-a2d3-307c36d7b48b" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_92ed1a98-c849-413c-a2d3-307c36d7b48b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_08db5744-804e-44e5-8c08-7ffd3f8fe2fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_92ed1a98-c849-413c-a2d3-307c36d7b48b" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_08db5744-804e-44e5-8c08-7ffd3f8fe2fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_1f0ef9e8-d176-419b-8372-e28932e85553" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_08db5744-804e-44e5-8c08-7ffd3f8fe2fd" xlink:to="loc_us-gaap_LineOfCreditMember_1f0ef9e8-d176-419b-8372-e28932e85553" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_9389f90b-ea29-4fff-ab62-18949131f13d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_32370ccb-93f6-4432-b7b9-6dbee3aaeafc" xlink:to="loc_us-gaap_DebtInstrumentAxis_9389f90b-ea29-4fff-ab62-18949131f13d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9389f90b-ea29-4fff-ab62-18949131f13d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_9389f90b-ea29-4fff-ab62-18949131f13d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_9389f90b-ea29-4fff-ab62-18949131f13d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_d998c04c-1d5c-4327-81aa-62beeda91002" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_9389f90b-ea29-4fff-ab62-18949131f13d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_d998c04c-1d5c-4327-81aa-62beeda91002" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_VariableRateTermLoanFacilitiesDueApril2027Member_82f60824-7cb4-40e8-bf8c-a3734d7a579d" xlink:href="fi-20251231.xsd#fi_VariableRateTermLoanFacilitiesDueApril2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_d998c04c-1d5c-4327-81aa-62beeda91002" xlink:to="loc_fi_VariableRateTermLoanFacilitiesDueApril2027Member_82f60824-7cb4-40e8-bf8c-a3734d7a579d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_VariableRateRevolvingCreditFacilitiesDueApril2027Member_7b43fb17-95cd-4eed-b49c-498ef4e25581" xlink:href="fi-20251231.xsd#fi_VariableRateRevolvingCreditFacilitiesDueApril2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_d998c04c-1d5c-4327-81aa-62beeda91002" xlink:to="loc_fi_VariableRateRevolvingCreditFacilitiesDueApril2027Member_7b43fb17-95cd-4eed-b49c-498ef4e25581" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_a533d379-a7e0-4a6a-9c72-c3b91e2917cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_32370ccb-93f6-4432-b7b9-6dbee3aaeafc" xlink:to="loc_us-gaap_CreditFacilityAxis_a533d379-a7e0-4a6a-9c72-c3b91e2917cf" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_a533d379-a7e0-4a6a-9c72-c3b91e2917cf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_a533d379-a7e0-4a6a-9c72-c3b91e2917cf" xlink:to="loc_us-gaap_CreditFacilityDomain_a533d379-a7e0-4a6a-9c72-c3b91e2917cf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_af20d424-9f48-4228-87cb-86f59e3b30c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_a533d379-a7e0-4a6a-9c72-c3b91e2917cf" xlink:to="loc_us-gaap_CreditFacilityDomain_af20d424-9f48-4228-87cb-86f59e3b30c8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_TermLoanFacilitiesMember_cc622b89-5d04-4fc7-ac4a-ba9e6ede7ebf" xlink:href="fi-20251231.xsd#fi_TermLoanFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_af20d424-9f48-4228-87cb-86f59e3b30c8" xlink:to="loc_fi_TermLoanFacilitiesMember_cc622b89-5d04-4fc7-ac4a-ba9e6ede7ebf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_a3dc937c-e3fb-45e0-adc5-7f7699cae9a4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_af20d424-9f48-4228-87cb-86f59e3b30c8" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_a3dc937c-e3fb-45e0-adc5-7f7699cae9a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_4b8de49e-8292-4bbf-ba4f-22f0e813e254" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_us-gaap_EquityMethodInvestments_4b8de49e-8292-4bbf-ba4f-22f0e813e254" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_50afec61-34e8-47cc-b0d1-9db4c2871ab1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_50afec61-34e8-47cc-b0d1-9db4c2871ab1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfInterestInJointVenture_e580764b-8d7d-49dd-b720-eac9c7981d47" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromDivestitureOfInterestInJointVenture"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfInterestInJointVenture_e580764b-8d7d-49dd-b720-eac9c7981d47" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment_db027535-d649-47bc-97e3-b78396ea46a1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment_db027535-d649-47bc-97e3-b78396ea46a1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_e4cf225f-b264-4e8b-afd6-23b825d8df7e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_e4cf225f-b264-4e8b-afd6-23b825d8df7e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_557daee5-cf1a-43b0-8c3a-e65487a1c744" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_557daee5-cf1a-43b0-8c3a-e65487a1c744" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_792ef567-2641-4dae-836d-f0db8d2ed8f4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_792ef567-2641-4dae-836d-f0db8d2ed8f4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_98d15a2f-ff0d-4a47-b813-6738625d2407" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_us-gaap_LongTermDebt_98d15a2f-ff0d-4a47-b813-6738625d2407" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_ProceedsFromEquityMethodInvestmentDistributionOperatingAndInvestingActivities_ceea6a14-b41e-4b05-a069-b1784912ce68" xlink:href="fi-20251231.xsd#fi_ProceedsFromEquityMethodInvestmentDistributionOperatingAndInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_fi_ProceedsFromEquityMethodInvestmentDistributionOperatingAndInvestingActivities_ceea6a14-b41e-4b05-a069-b1784912ce68" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital_d2262b72-4494-401e-9c25-237c659a7f31" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_us-gaap_ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital_d2262b72-4494-401e-9c25-237c659a7f31" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal_019be6a6-ffa8-7b74-9f92-3e43e4defa7a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_us-gaap_EquityMethodInvestmentRealizedGainLossOnDisposal_019be6a6-ffa8-7b74-9f92-3e43e4defa7a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_775e4f10-2bbc-4bc8-a6d9-cac1d18b7a36" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_775e4f10-2bbc-4bc8-a6d9-cac1d18b7a36" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount_2f8b2b29-6d99-4c0d-b18e-4f21da990540" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount_2f8b2b29-6d99-4c0d-b18e-4f21da990540" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi_019be6a6-7e65-7274-b1b6-790c37dfa657" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_94a9f2e4-2a71-4be2-ba10-ec06fe500a88" xlink:to="loc_us-gaap_ProceedsFromSaleOfEquitySecuritiesFvNi_019be6a6-7e65-7274-b1b6-790c37dfa657" xlink:type="arc" order="13"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/DerivativesandHedgingInstrumentsNarrativeDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#DerivativesandHedgingInstrumentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/DerivativesandHedgingInstrumentsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_aaaa87a8-8f2e-4ba9-88bb-8fdd374dd75f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_07bb19fa-f49c-436c-94ca-09fc4f53e135" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_aaaa87a8-8f2e-4ba9-88bb-8fdd374dd75f" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_07bb19fa-f49c-436c-94ca-09fc4f53e135" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CurrencyAxis_587425dd-1b12-47de-8505-a52149c04fb1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CurrencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_07bb19fa-f49c-436c-94ca-09fc4f53e135" xlink:to="loc_srt_CurrencyAxis_587425dd-1b12-47de-8505-a52149c04fb1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_587425dd-1b12-47de-8505-a52149c04fb1_default" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CurrencyAxis_587425dd-1b12-47de-8505-a52149c04fb1" xlink:to="loc_currency_AllCurrenciesDomain_587425dd-1b12-47de-8505-a52149c04fb1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_ae86ef0b-291b-4b44-9a05-aa5f273a7e51" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CurrencyAxis_587425dd-1b12-47de-8505-a52149c04fb1" xlink:to="loc_currency_AllCurrenciesDomain_ae86ef0b-291b-4b44-9a05-aa5f273a7e51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_INR_7c922da1-73d7-42cd-82a4-7cda360a6702" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_INR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_ae86ef0b-291b-4b44-9a05-aa5f273a7e51" xlink:to="loc_currency_INR_7c922da1-73d7-42cd-82a4-7cda360a6702" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_GBP_254889c2-a83d-4266-b0a4-150b1ad10eb5" xlink:href="https://xbrl.sec.gov/currency/2025/currency-2025.xsd#currency_GBP"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_ae86ef0b-291b-4b44-9a05-aa5f273a7e51" xlink:to="loc_currency_GBP_254889c2-a83d-4266-b0a4-150b1ad10eb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_40a05450-981d-45e0-bb5e-5c491dde0fdb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_07bb19fa-f49c-436c-94ca-09fc4f53e135" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_40a05450-981d-45e0-bb5e-5c491dde0fdb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_40a05450-981d-45e0-bb5e-5c491dde0fdb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_40a05450-981d-45e0-bb5e-5c491dde0fdb" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_40a05450-981d-45e0-bb5e-5c491dde0fdb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_98c7ebbc-0e72-4985-ab0f-5bca6b3bf135" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_40a05450-981d-45e0-bb5e-5c491dde0fdb" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_98c7ebbc-0e72-4985-ab0f-5bca6b3bf135" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_580e40e4-9817-40aa-91fc-9f5c736b14d1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_98c7ebbc-0e72-4985-ab0f-5bca6b3bf135" xlink:to="loc_us-gaap_ForeignExchangeContractMember_580e40e4-9817-40aa-91fc-9f5c736b14d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryLockMember_bba20f32-6209-4392-9e1c-6c789b38d651" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryLockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_98c7ebbc-0e72-4985-ab0f-5bca6b3bf135" xlink:to="loc_us-gaap_TreasuryLockMember_bba20f32-6209-4392-9e1c-6c789b38d651" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CrossCurrencyInterestRateContractMember_43c32d3b-75f2-4659-b018-64ec1e353de9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CrossCurrencyInterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_98c7ebbc-0e72-4985-ab0f-5bca6b3bf135" xlink:to="loc_us-gaap_CrossCurrencyInterestRateContractMember_43c32d3b-75f2-4659-b018-64ec1e353de9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_28eae7ba-ea4d-40c7-b11c-88115f0d888a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_07bb19fa-f49c-436c-94ca-09fc4f53e135" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_28eae7ba-ea4d-40c7-b11c-88115f0d888a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_28eae7ba-ea4d-40c7-b11c-88115f0d888a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_28eae7ba-ea4d-40c7-b11c-88115f0d888a" xlink:to="loc_us-gaap_HedgingRelationshipDomain_28eae7ba-ea4d-40c7-b11c-88115f0d888a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_bb89c7f4-de71-47aa-8c37-0ac5bb39f4af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_28eae7ba-ea4d-40c7-b11c-88115f0d888a" xlink:to="loc_us-gaap_HedgingRelationshipDomain_bb89c7f4-de71-47aa-8c37-0ac5bb39f4af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentHedgingMember_82d66a74-7dcb-4a47-86db-5430e3d5841a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetInvestmentHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_bb89c7f4-de71-47aa-8c37-0ac5bb39f4af" xlink:to="loc_us-gaap_NetInvestmentHedgingMember_82d66a74-7dcb-4a47-86db-5430e3d5841a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_106be4de-311e-40a1-ab24-893aeb248c28" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_07bb19fa-f49c-436c-94ca-09fc4f53e135" xlink:to="loc_us-gaap_DebtInstrumentAxis_106be4de-311e-40a1-ab24-893aeb248c28" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_106be4de-311e-40a1-ab24-893aeb248c28_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_106be4de-311e-40a1-ab24-893aeb248c28" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_106be4de-311e-40a1-ab24-893aeb248c28_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_89b4f7bc-4423-4e02-a391-6a4271576468" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_106be4de-311e-40a1-ab24-893aeb248c28" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_89b4f7bc-4423-4e02-a391-6a4271576468" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A2.25SeniorNotesDueJuly2025Member_f07e6a06-5d13-4133-aed3-11df34e6aefe" xlink:href="fi-20251231.xsd#fi_A2.25SeniorNotesDueJuly2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_89b4f7bc-4423-4e02-a391-6a4271576468" xlink:to="loc_fi_A2.25SeniorNotesDueJuly2025Member_f07e6a06-5d13-4133-aed3-11df34e6aefe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_00d62968-6bf2-4c62-8cf9-4c2dfa2d7ef2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_07bb19fa-f49c-436c-94ca-09fc4f53e135" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_00d62968-6bf2-4c62-8cf9-4c2dfa2d7ef2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_00d62968-6bf2-4c62-8cf9-4c2dfa2d7ef2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_00d62968-6bf2-4c62-8cf9-4c2dfa2d7ef2" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_00d62968-6bf2-4c62-8cf9-4c2dfa2d7ef2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_f206ee13-3100-4e1c-aca4-555fa9036416" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_00d62968-6bf2-4c62-8cf9-4c2dfa2d7ef2" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_f206ee13-3100-4e1c-aca4-555fa9036416" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_3c3ffc69-ac07-436a-ad24-63e66dc310c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_f206ee13-3100-4e1c-aca4-555fa9036416" xlink:to="loc_us-gaap_SeniorNotesMember_3c3ffc69-ac07-436a-ad24-63e66dc310c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_6783ef5b-2e3b-4d55-8918-eb95abe6a1ec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_aaaa87a8-8f2e-4ba9-88bb-8fdd374dd75f" xlink:to="loc_us-gaap_DerivativeNotionalAmount_6783ef5b-2e3b-4d55-8918-eb95abe6a1ec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months_a7f8bd60-b237-4cde-8a7c-072f1ed3ce21" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_aaaa87a8-8f2e-4ba9-88bb-8fdd374dd75f" xlink:to="loc_us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months_a7f8bd60-b237-4cde-8a7c-072f1ed3ce21" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_fff08ce2-7e2a-43c5-93f4-6fcb27d8b65f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_aaaa87a8-8f2e-4ba9-88bb-8fdd374dd75f" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_fff08ce2-7e2a-43c5-93f4-6fcb27d8b65f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet_c457e74b-e2cd-411f-9f59-a4a07f63359d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_aaaa87a8-8f2e-4ba9-88bb-8fdd374dd75f" xlink:to="loc_us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet_c457e74b-e2cd-411f-9f59-a4a07f63359d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_cece500a-1444-48f5-8770-a2935632cdc1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_aaaa87a8-8f2e-4ba9-88bb-8fdd374dd75f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_cece500a-1444-48f5-8770-a2935632cdc1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_36f34858-c255-4905-98d6-0a5381d5e883" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_aaaa87a8-8f2e-4ba9-88bb-8fdd374dd75f" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_36f34858-c255-4905-98d6-0a5381d5e883" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_f1edee2b-af49-49e4-99cb-b3bf21582b69" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_aaaa87a8-8f2e-4ba9-88bb-8fdd374dd75f" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_f1edee2b-af49-49e4-99cb-b3bf21582b69" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/DerivativesandHedgingInstrumentsScheduleofNotionalAmountsofRateSwapContractsDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#DerivativesandHedgingInstrumentsScheduleofNotionalAmountsofRateSwapContractsDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/DerivativesandHedgingInstrumentsScheduleofNotionalAmountsofRateSwapContractsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_74915640-567d-450f-8b7b-193abc968cb7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_bccad641-62eb-4d50-83dd-e291a86cd4c6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_74915640-567d-450f-8b7b-193abc968cb7" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_bccad641-62eb-4d50-83dd-e291a86cd4c6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_080cb7da-feca-46f8-824a-ab18bb7c51d6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_bccad641-62eb-4d50-83dd-e291a86cd4c6" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_080cb7da-feca-46f8-824a-ab18bb7c51d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_080cb7da-feca-46f8-824a-ab18bb7c51d6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_080cb7da-feca-46f8-824a-ab18bb7c51d6" xlink:to="loc_us-gaap_HedgingRelationshipDomain_080cb7da-feca-46f8-824a-ab18bb7c51d6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_dc78b73a-3ff5-4873-9870-deba4f89947a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_080cb7da-feca-46f8-824a-ab18bb7c51d6" xlink:to="loc_us-gaap_HedgingRelationshipDomain_dc78b73a-3ff5-4873-9870-deba4f89947a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentHedgingMember_a45959e8-c6d3-43fc-aa3f-514a60c78d33" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetInvestmentHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_dc78b73a-3ff5-4873-9870-deba4f89947a" xlink:to="loc_us-gaap_NetInvestmentHedgingMember_a45959e8-c6d3-43fc-aa3f-514a60c78d33" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_39d8c9fd-286c-4d3c-bebc-ae7cd4d0f20a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_74915640-567d-450f-8b7b-193abc968cb7" xlink:to="loc_us-gaap_DerivativeNotionalAmount_39d8c9fd-286c-4d3c-bebc-ae7cd4d0f20a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/DerivativesandHedgingInstrumentsScheduleofNetInvestmentHedgesinAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#DerivativesandHedgingInstrumentsScheduleofNetInvestmentHedgesinAccumulatedOtherComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/DerivativesandHedgingInstrumentsScheduleofNetInvestmentHedgesinAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_2485024e-09ad-497a-b49f-03f1bc97bbc7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_6f5a8c20-2d3a-4d23-8619-e7d472ddf88c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_2485024e-09ad-497a-b49f-03f1bc97bbc7" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_6f5a8c20-2d3a-4d23-8619-e7d472ddf88c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_2e7c9809-5b04-4411-9861-368f608dadf7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_6f5a8c20-2d3a-4d23-8619-e7d472ddf88c" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_2e7c9809-5b04-4411-9861-368f608dadf7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_2e7c9809-5b04-4411-9861-368f608dadf7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_2e7c9809-5b04-4411-9861-368f608dadf7" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_2e7c9809-5b04-4411-9861-368f608dadf7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_d4982fe2-6794-4b4b-8f84-9ef9689f0ab3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_2e7c9809-5b04-4411-9861-368f608dadf7" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_d4982fe2-6794-4b4b-8f84-9ef9689f0ab3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CrossCurrencyInterestRateContractMember_684679ff-2ba8-409c-a6ea-1e4c8a4ed5ff" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CrossCurrencyInterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_d4982fe2-6794-4b4b-8f84-9ef9689f0ab3" xlink:to="loc_us-gaap_CrossCurrencyInterestRateContractMember_684679ff-2ba8-409c-a6ea-1e4c8a4ed5ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_ForeignCurrencyDenominatedDebtMember_0321029a-70db-4f21-906c-3d84baf0cf29" xlink:href="fi-20251231.xsd#fi_ForeignCurrencyDenominatedDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_d4982fe2-6794-4b4b-8f84-9ef9689f0ab3" xlink:to="loc_fi_ForeignCurrencyDenominatedDebtMember_0321029a-70db-4f21-906c-3d84baf0cf29" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_6ad910bc-c9c8-437e-a652-640597dcac6e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_6f5a8c20-2d3a-4d23-8619-e7d472ddf88c" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_6ad910bc-c9c8-437e-a652-640597dcac6e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_6ad910bc-c9c8-437e-a652-640597dcac6e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_6ad910bc-c9c8-437e-a652-640597dcac6e" xlink:to="loc_us-gaap_HedgingRelationshipDomain_6ad910bc-c9c8-437e-a652-640597dcac6e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_e7fb7110-ce19-45fe-9a50-0ede5b0253f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_6ad910bc-c9c8-437e-a652-640597dcac6e" xlink:to="loc_us-gaap_HedgingRelationshipDomain_e7fb7110-ce19-45fe-9a50-0ede5b0253f0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentHedgingMember_b05646dd-c4ad-4c08-bb70-6c5bb0cdb73a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetInvestmentHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_e7fb7110-ce19-45fe-9a50-0ede5b0253f0" xlink:to="loc_us-gaap_NetInvestmentHedgingMember_b05646dd-c4ad-4c08-bb70-6c5bb0cdb73a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_becc2b66-f30c-4372-a4c1-c6f3f1dca000" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_2485024e-09ad-497a-b49f-03f1bc97bbc7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_becc2b66-f30c-4372-a4c1-c6f3f1dca000" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/FairValueMeasurementsAssetsandLiabilitiesMeasuredatFairValueOnaRecurringBasisDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#FairValueMeasurementsAssetsandLiabilitiesMeasuredatFairValueOnaRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/FairValueMeasurementsAssetsandLiabilitiesMeasuredatFairValueOnaRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLineItems_9e81fba5-9a05-4766-b540-802b76fa8ad7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable_e62e59d7-ee03-4eea-9cd9-d7fc1f10d907" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLineItems_9e81fba5-9a05-4766-b540-802b76fa8ad7" xlink:to="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable_e62e59d7-ee03-4eea-9cd9-d7fc1f10d907" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_45e71f14-5060-45cc-82f0-cd223e906686" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable_e62e59d7-ee03-4eea-9cd9-d7fc1f10d907" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_45e71f14-5060-45cc-82f0-cd223e906686" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_45e71f14-5060-45cc-82f0-cd223e906686_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_45e71f14-5060-45cc-82f0-cd223e906686" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_45e71f14-5060-45cc-82f0-cd223e906686_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_d99bc0b2-e91f-411f-b07e-f065ffa6e018" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_45e71f14-5060-45cc-82f0-cd223e906686" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_d99bc0b2-e91f-411f-b07e-f065ffa6e018" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_1c0abb0e-743d-49b8-9b8f-51bb0794d65d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_d99bc0b2-e91f-411f-b07e-f065ffa6e018" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_1c0abb0e-743d-49b8-9b8f-51bb0794d65d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_42809420-1c4d-4b9c-8b59-45a5ced9a9f9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable_e62e59d7-ee03-4eea-9cd9-d7fc1f10d907" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_42809420-1c4d-4b9c-8b59-45a5ced9a9f9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_42809420-1c4d-4b9c-8b59-45a5ced9a9f9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_42809420-1c4d-4b9c-8b59-45a5ced9a9f9" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_42809420-1c4d-4b9c-8b59-45a5ced9a9f9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_f88a1f34-cd1c-4c45-a923-3a239cdd34ab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_42809420-1c4d-4b9c-8b59-45a5ced9a9f9" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_f88a1f34-cd1c-4c45-a923-3a239cdd34ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_4544a72e-4860-4902-9286-b8e3e0da49fd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_f88a1f34-cd1c-4c45-a923-3a239cdd34ab" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_4544a72e-4860-4902-9286-b8e3e0da49fd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_3fe2e84a-9e71-4ecf-9d0f-620af1d62387" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_f88a1f34-cd1c-4c45-a923-3a239cdd34ab" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_3fe2e84a-9e71-4ecf-9d0f-620af1d62387" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_c0396693-7406-449a-bd74-cbe9dd41dfcd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable_e62e59d7-ee03-4eea-9cd9-d7fc1f10d907" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_c0396693-7406-449a-bd74-cbe9dd41dfcd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_c0396693-7406-449a-bd74-cbe9dd41dfcd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_c0396693-7406-449a-bd74-cbe9dd41dfcd" xlink:to="loc_us-gaap_HedgingRelationshipDomain_c0396693-7406-449a-bd74-cbe9dd41dfcd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_4bb3f277-bfab-4159-ae02-dbbcb5f71c70" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_c0396693-7406-449a-bd74-cbe9dd41dfcd" xlink:to="loc_us-gaap_HedgingRelationshipDomain_4bb3f277-bfab-4159-ae02-dbbcb5f71c70" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_36a83401-d5ff-47ac-a712-1907758efc38" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_4bb3f277-bfab-4159-ae02-dbbcb5f71c70" xlink:to="loc_us-gaap_CashFlowHedgingMember_36a83401-d5ff-47ac-a712-1907758efc38" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentHedgingMember_04c33e4a-731d-44d9-b368-e5c42ab1c46b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetInvestmentHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_4bb3f277-bfab-4159-ae02-dbbcb5f71c70" xlink:to="loc_us-gaap_NetInvestmentHedgingMember_04c33e4a-731d-44d9-b368-e5c42ab1c46b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueHedgingMember_c8a01ad1-1714-43e7-b1db-6c2fc1b21178" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_4bb3f277-bfab-4159-ae02-dbbcb5f71c70" xlink:to="loc_us-gaap_FairValueHedgingMember_c8a01ad1-1714-43e7-b1db-6c2fc1b21178" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_5024c468-9222-4b22-aa06-06f06ef26412" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable_e62e59d7-ee03-4eea-9cd9-d7fc1f10d907" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_5024c468-9222-4b22-aa06-06f06ef26412" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_5024c468-9222-4b22-aa06-06f06ef26412_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_5024c468-9222-4b22-aa06-06f06ef26412" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_5024c468-9222-4b22-aa06-06f06ef26412_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_7c8fe62c-ddcb-4e59-b91f-4a8cc5dc82c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_5024c468-9222-4b22-aa06-06f06ef26412" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_7c8fe62c-ddcb-4e59-b91f-4a8cc5dc82c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CrossCurrencyInterestRateContractMember_266dd7e1-96a5-4430-9bba-7cb6df5916cf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CrossCurrencyInterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7c8fe62c-ddcb-4e59-b91f-4a8cc5dc82c9" xlink:to="loc_us-gaap_CrossCurrencyInterestRateContractMember_266dd7e1-96a5-4430-9bba-7cb6df5916cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_9f951157-39f5-410c-827e-4b16a794b55f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7c8fe62c-ddcb-4e59-b91f-4a8cc5dc82c9" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_9f951157-39f5-410c-827e-4b16a794b55f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_a07e4ea1-7525-46c5-8fb9-7ecece219592" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLineItems_9e81fba5-9a05-4766-b540-802b76fa8ad7" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_a07e4ea1-7525-46c5-8fb9-7ecece219592" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsCurrent_167604d4-dbc6-47d2-a3d5-63ab2f9fbff1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_a07e4ea1-7525-46c5-8fb9-7ecece219592" xlink:to="loc_us-gaap_DerivativeAssetsCurrent_167604d4-dbc6-47d2-a3d5-63ab2f9fbff1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsNoncurrent_301cdff8-a0d6-4e41-ab8f-96bb993f1041" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_a07e4ea1-7525-46c5-8fb9-7ecece219592" xlink:to="loc_us-gaap_DerivativeAssetsNoncurrent_301cdff8-a0d6-4e41-ab8f-96bb993f1041" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_866cd1d0-0652-4986-b989-d9e2bc465971" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLineItems_9e81fba5-9a05-4766-b540-802b76fa8ad7" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_866cd1d0-0652-4986-b989-d9e2bc465971" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesCurrent_e7c03e51-9495-43f0-8fc2-5bb800bbda36" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_866cd1d0-0652-4986-b989-d9e2bc465971" xlink:to="loc_us-gaap_DerivativeLiabilitiesCurrent_e7c03e51-9495-43f0-8fc2-5bb800bbda36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesNoncurrent_6201f5b3-6f43-46fa-aefc-eb23d6dbc0eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DerivativeLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_866cd1d0-0652-4986-b989-d9e2bc465971" xlink:to="loc_us-gaap_DerivativeLiabilitiesNoncurrent_6201f5b3-6f43-46fa-aefc-eb23d6dbc0eb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_a62e8a6f-ee60-410e-851c-fca742498724" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_866cd1d0-0652-4986-b989-d9e2bc465971" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_a62e8a6f-ee60-410e-851c-fca742498724" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_7caf3e89-efa8-4c58-9178-17ce9b0aa619" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_866cd1d0-0652-4986-b989-d9e2bc465971" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_7caf3e89-efa8-4c58-9178-17ce9b0aa619" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MandatorilyRedeemablePreferredStockFairValueDisclosure_a25f279f-bc94-478d-a842-bb098ab193f4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MandatorilyRedeemablePreferredStockFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_866cd1d0-0652-4986-b989-d9e2bc465971" xlink:to="loc_us-gaap_MandatorilyRedeemablePreferredStockFairValueDisclosure_a25f279f-bc94-478d-a842-bb098ab193f4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteesFairValueDisclosure_3a806f5e-a938-4636-ae9b-9f09a31f840d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GuaranteesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_866cd1d0-0652-4986-b989-d9e2bc465971" xlink:to="loc_us-gaap_GuaranteesFairValueDisclosure_3a806f5e-a938-4636-ae9b-9f09a31f840d" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/FairValueMeasurementsNarrativeDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#FairValueMeasurementsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/FairValueMeasurementsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLineItems_609f22b4-da1b-4118-bd3a-93a19430bd78" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable_b044fcc0-9f82-4e7b-9d46-d6eb7ee0cd79" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLineItems_609f22b4-da1b-4118-bd3a-93a19430bd78" xlink:to="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable_b044fcc0-9f82-4e7b-9d46-d6eb7ee0cd79" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis_917cbb5a-f8bc-4a54-827a-394a969fe564" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GuaranteeObligationsByNatureAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable_b044fcc0-9f82-4e7b-9d46-d6eb7ee0cd79" xlink:to="loc_us-gaap_GuaranteeObligationsByNatureAxis_917cbb5a-f8bc-4a54-827a-394a969fe564" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_917cbb5a-f8bc-4a54-827a-394a969fe564_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_917cbb5a-f8bc-4a54-827a-394a969fe564" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_917cbb5a-f8bc-4a54-827a-394a969fe564_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_acafed19-d204-404f-82d8-825f0ecb0ad1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_917cbb5a-f8bc-4a54-827a-394a969fe564" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_acafed19-d204-404f-82d8-825f0ecb0ad1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialGuaranteeMember_bfd13bb6-4352-41d2-b059-1104b5135e55" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinancialGuaranteeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_acafed19-d204-404f-82d8-825f0ecb0ad1" xlink:to="loc_us-gaap_FinancialGuaranteeMember_bfd13bb6-4352-41d2-b059-1104b5135e55" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0e7bfd60-d9df-4b5b-a978-a907bd1cd6c4" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable_b044fcc0-9f82-4e7b-9d46-d6eb7ee0cd79" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0e7bfd60-d9df-4b5b-a978-a907bd1cd6c4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_0e7bfd60-d9df-4b5b-a978-a907bd1cd6c4_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0e7bfd60-d9df-4b5b-a978-a907bd1cd6c4" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_0e7bfd60-d9df-4b5b-a978-a907bd1cd6c4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_d66ef189-4e9c-4c59-b45a-1444ae391402" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_0e7bfd60-d9df-4b5b-a978-a907bd1cd6c4" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_d66ef189-4e9c-4c59-b45a-1444ae391402" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_LendingSolutionsBusinessMember_94ce1572-b473-4828-9b8d-67946ebb10b8" xlink:href="fi-20251231.xsd#fi_LendingSolutionsBusinessMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_d66ef189-4e9c-4c59-b45a-1444ae391402" xlink:to="loc_fi_LendingSolutionsBusinessMember_94ce1572-b473-4828-9b8d-67946ebb10b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_08c6d226-b5f3-4549-ac64-9854bac7cdbc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable_b044fcc0-9f82-4e7b-9d46-d6eb7ee0cd79" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_08c6d226-b5f3-4549-ac64-9854bac7cdbc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_08c6d226-b5f3-4549-ac64-9854bac7cdbc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_08c6d226-b5f3-4549-ac64-9854bac7cdbc" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_08c6d226-b5f3-4549-ac64-9854bac7cdbc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c0430048-1b0f-4190-9e3a-d23a064118c4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_08c6d226-b5f3-4549-ac64-9854bac7cdbc" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c0430048-1b0f-4190-9e3a-d23a064118c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_03fcd2cf-0f28-4a75-b566-513a55db7c61" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_c0430048-1b0f-4190-9e3a-d23a064118c4" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_03fcd2cf-0f28-4a75-b566-513a55db7c61" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_fa48eb58-557e-432d-9bf5-e37b1a02ac56" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable_b044fcc0-9f82-4e7b-9d46-d6eb7ee0cd79" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_fa48eb58-557e-432d-9bf5-e37b1a02ac56" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_fa48eb58-557e-432d-9bf5-e37b1a02ac56_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_fa48eb58-557e-432d-9bf5-e37b1a02ac56" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_fa48eb58-557e-432d-9bf5-e37b1a02ac56_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_bcdda3e5-69c7-4c7d-9ad1-a1db1c4c3da9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_fa48eb58-557e-432d-9bf5-e37b1a02ac56" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_bcdda3e5-69c7-4c7d-9ad1-a1db1c4c3da9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_ab943ccc-eed0-4783-9e1c-f38431b7e935" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_bcdda3e5-69c7-4c7d-9ad1-a1db1c4c3da9" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_ab943ccc-eed0-4783-9e1c-f38431b7e935" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_3c3dd1fb-761b-49dd-8268-d0bc9c04881b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_ab943ccc-eed0-4783-9e1c-f38431b7e935" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_3c3dd1fb-761b-49dd-8268-d0bc9c04881b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_82be407a-384d-44cb-9cd7-e8b5dc141ddd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_ab943ccc-eed0-4783-9e1c-f38431b7e935" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_82be407a-384d-44cb-9cd7-e8b5dc141ddd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_703a0f8f-81b1-4105-9df6-55ec1e42336a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareTable_b044fcc0-9f82-4e7b-9d46-d6eb7ee0cd79" xlink:to="loc_dei_LegalEntityAxis_703a0f8f-81b1-4105-9df6-55ec1e42336a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_703a0f8f-81b1-4105-9df6-55ec1e42336a_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_703a0f8f-81b1-4105-9df6-55ec1e42336a" xlink:to="loc_dei_EntityDomain_703a0f8f-81b1-4105-9df6-55ec1e42336a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_9edf7059-09aa-43e2-be14-33f3f82d3397" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_703a0f8f-81b1-4105-9df6-55ec1e42336a" xlink:to="loc_dei_EntityDomain_9edf7059-09aa-43e2-be14-33f3f82d3397" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_LendingJointVenturesMember_0b1aa61f-0c37-4fa3-98bf-c7f53736fcc1" xlink:href="fi-20251231.xsd#fi_LendingJointVenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_9edf7059-09aa-43e2-be14-33f3f82d3397" xlink:to="loc_fi_LendingJointVenturesMember_0b1aa61f-0c37-4fa3-98bf-c7f53736fcc1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFairValue_59e173a4-0fb1-40f3-a32e-92e6a6d11411" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLineItems_609f22b4-da1b-4118-bd3a-93a19430bd78" xlink:to="loc_us-gaap_DebtInstrumentFairValue_59e173a4-0fb1-40f3-a32e-92e6a6d11411" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_ed3cf46b-2443-4a7f-86d8-042f5ed1552b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLineItems_609f22b4-da1b-4118-bd3a-93a19430bd78" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_ed3cf46b-2443-4a7f-86d8-042f5ed1552b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsCurrentCarryingValue_09d36f8f-1ffc-4365-b362-c5dc53728d6f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GuaranteeObligationsCurrentCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareLineItems_609f22b4-da1b-4118-bd3a-93a19430bd78" xlink:to="loc_us-gaap_GuaranteeObligationsCurrentCarryingValue_09d36f8f-1ffc-4365-b362-c5dc53728d6f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/LeasesNarrativeDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#LeasesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/LeasesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_19fd9329-3e12-49e4-b41c-b9b0621cd675" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_2dbd17e4-bfc6-46e7-9ac5-b1b05d8f7f87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_19fd9329-3e12-49e4-b41c-b9b0621cd675" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_2dbd17e4-bfc6-46e7-9ac5-b1b05d8f7f87" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_516af334-edfb-4cd7-96ee-d50c162e3423" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_2dbd17e4-bfc6-46e7-9ac5-b1b05d8f7f87" xlink:to="loc_srt_RangeAxis_516af334-edfb-4cd7-96ee-d50c162e3423" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_516af334-edfb-4cd7-96ee-d50c162e3423_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_516af334-edfb-4cd7-96ee-d50c162e3423" xlink:to="loc_srt_RangeMember_516af334-edfb-4cd7-96ee-d50c162e3423_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_cecdbae9-9100-42cb-950e-8a6d8d07200b" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_516af334-edfb-4cd7-96ee-d50c162e3423" xlink:to="loc_srt_RangeMember_cecdbae9-9100-42cb-950e-8a6d8d07200b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_0ac2d9f9-f0af-472e-8cab-4883eefe7c3f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_cecdbae9-9100-42cb-950e-8a6d8d07200b" xlink:to="loc_srt_MinimumMember_0ac2d9f9-f0af-472e-8cab-4883eefe7c3f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_9a763b7d-7e65-44a2-8f57-afab48658049" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_cecdbae9-9100-42cb-950e-8a6d8d07200b" xlink:to="loc_srt_MaximumMember_9a763b7d-7e65-44a2-8f57-afab48658049" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_724f851b-4095-48ec-8dcb-5af06a584e1d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseRemainingLeaseTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_19fd9329-3e12-49e4-b41c-b9b0621cd675" xlink:to="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_724f851b-4095-48ec-8dcb-5af06a584e1d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeFinanceLeaseRemainingLeaseTerm_ec2c9123-4478-40d8-9234-eb2d6a28ebca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeFinanceLeaseRemainingLeaseTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_19fd9329-3e12-49e4-b41c-b9b0621cd675" xlink:to="loc_us-gaap_LesseeFinanceLeaseRemainingLeaseTerm_ec2c9123-4478-40d8-9234-eb2d6a28ebca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LessorOperatingLeaseTermOfContract_505546fe-5aa2-4df8-8cb6-d94cdd793f6b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LessorOperatingLeaseTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_19fd9329-3e12-49e4-b41c-b9b0621cd675" xlink:to="loc_us-gaap_LessorOperatingLeaseTermOfContract_505546fe-5aa2-4df8-8cb6-d94cdd793f6b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LessorSalesTypeLeaseTermOfContract1_468223c1-108f-4418-b498-ccb26f2b9448" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LessorSalesTypeLeaseTermOfContract1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_19fd9329-3e12-49e4-b41c-b9b0621cd675" xlink:to="loc_us-gaap_LessorSalesTypeLeaseTermOfContract1_468223c1-108f-4418-b498-ccb26f2b9448" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetInvestmentInLeaseAllowanceForCreditLossExcludingAccruedInterest_0164032e-becc-40c0-ac87-d4cc16375159" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetInvestmentInLeaseAllowanceForCreditLossExcludingAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_19fd9329-3e12-49e4-b41c-b9b0621cd675" xlink:to="loc_us-gaap_NetInvestmentInLeaseAllowanceForCreditLossExcludingAccruedInterest_0164032e-becc-40c0-ac87-d4cc16375159" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/LeasesLeaseMaturityDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#LeasesLeaseMaturityDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/LeasesLeaseMaturityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_18f28981-aa97-46b9-83fc-2b32923fb6e8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_e0d28a52-df05-48cc-9d5d-4eec221f91f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_18f28981-aa97-46b9-83fc-2b32923fb6e8" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_e0d28a52-df05-48cc-9d5d-4eec221f91f0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_4c88aa50-e50b-4ad7-a50b-38905d617122" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_e0d28a52-df05-48cc-9d5d-4eec221f91f0" xlink:to="loc_srt_RangeAxis_4c88aa50-e50b-4ad7-a50b-38905d617122" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_4c88aa50-e50b-4ad7-a50b-38905d617122_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_4c88aa50-e50b-4ad7-a50b-38905d617122" xlink:to="loc_srt_RangeMember_4c88aa50-e50b-4ad7-a50b-38905d617122_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_8c1c1a13-1985-4fe9-bb07-40ef13c7b444" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_4c88aa50-e50b-4ad7-a50b-38905d617122" xlink:to="loc_srt_RangeMember_8c1c1a13-1985-4fe9-bb07-40ef13c7b444" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_f080a5d3-9fa8-424a-994c-cba213dac36b" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_8c1c1a13-1985-4fe9-bb07-40ef13c7b444" xlink:to="loc_srt_MaximumMember_f080a5d3-9fa8-424a-994c-cba213dac36b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract_663b41b8-3751-4360-8bdd-e2fc81ebfae9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_18f28981-aa97-46b9-83fc-2b32923fb6e8" xlink:to="loc_us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract_663b41b8-3751-4360-8bdd-e2fc81ebfae9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_59526791-30d3-414e-a8db-7970349a283b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract_663b41b8-3751-4360-8bdd-e2fc81ebfae9" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_59526791-30d3-414e-a8db-7970349a283b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_9076a485-92f4-4732-ab3e-a9e942684961" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract_663b41b8-3751-4360-8bdd-e2fc81ebfae9" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_9076a485-92f4-4732-ab3e-a9e942684961" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_eee0b704-8ed3-488b-a0ec-a4e46312a0cb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract_663b41b8-3751-4360-8bdd-e2fc81ebfae9" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_eee0b704-8ed3-488b-a0ec-a4e46312a0cb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_ff39d958-b49c-40cf-906c-90262ce2d2ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract_663b41b8-3751-4360-8bdd-e2fc81ebfae9" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_ff39d958-b49c-40cf-906c-90262ce2d2ea" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_ffe11cf3-606f-4580-bdeb-d373d0b7f856" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract_663b41b8-3751-4360-8bdd-e2fc81ebfae9" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_ffe11cf3-606f-4580-bdeb-d373d0b7f856" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_50ab3046-3193-48a2-85a6-b7e77f04a394" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract_663b41b8-3751-4360-8bdd-e2fc81ebfae9" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_50ab3046-3193-48a2-85a6-b7e77f04a394" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_f626afaa-b815-49b8-9d4c-24ab98627c28" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract_663b41b8-3751-4360-8bdd-e2fc81ebfae9" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_f626afaa-b815-49b8-9d4c-24ab98627c28" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_3e4b5d38-d602-4aa7-b91b-b6b3b49a7345" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract_663b41b8-3751-4360-8bdd-e2fc81ebfae9" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_3e4b5d38-d602-4aa7-b91b-b6b3b49a7345" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_56919d8f-d7a9-4ec9-8804-28c3d20704f6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeaseLiabilitiesPaymentsDueAbstract_663b41b8-3751-4360-8bdd-e2fc81ebfae9" xlink:to="loc_us-gaap_OperatingLeaseLiability_56919d8f-d7a9-4ec9-8804-28c3d20704f6" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilitiesPaymentsDueAbstract_21eff9bf-863e-4251-80e9-e49a7a61a4dc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilitiesPaymentsDueAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_18f28981-aa97-46b9-83fc-2b32923fb6e8" xlink:to="loc_us-gaap_FinanceLeaseLiabilitiesPaymentsDueAbstract_21eff9bf-863e-4251-80e9-e49a7a61a4dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_a8b1ec82-af3e-4b93-bf67-fc98c5e5dcbd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinanceLeaseLiabilitiesPaymentsDueAbstract_21eff9bf-863e-4251-80e9-e49a7a61a4dc" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_a8b1ec82-af3e-4b93-bf67-fc98c5e5dcbd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_bc230136-1175-4b84-b4d5-b275584d2939" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinanceLeaseLiabilitiesPaymentsDueAbstract_21eff9bf-863e-4251-80e9-e49a7a61a4dc" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_bc230136-1175-4b84-b4d5-b275584d2939" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_cbfc53e8-7982-413e-8b79-e76967ffffc4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinanceLeaseLiabilitiesPaymentsDueAbstract_21eff9bf-863e-4251-80e9-e49a7a61a4dc" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_cbfc53e8-7982-413e-8b79-e76967ffffc4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_c2ee1cf6-f6b6-46b2-b1af-4aaaf69b0b0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinanceLeaseLiabilitiesPaymentsDueAbstract_21eff9bf-863e-4251-80e9-e49a7a61a4dc" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_c2ee1cf6-f6b6-46b2-b1af-4aaaf69b0b0b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive_572dbb28-f1d0-40ed-9fb3-845cb778385a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinanceLeaseLiabilitiesPaymentsDueAbstract_21eff9bf-863e-4251-80e9-e49a7a61a4dc" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive_572dbb28-f1d0-40ed-9fb3-845cb778385a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive_0e6ddd1c-c8ff-4f2e-a8d3-d547bd293b47" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinanceLeaseLiabilitiesPaymentsDueAbstract_21eff9bf-863e-4251-80e9-e49a7a61a4dc" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive_0e6ddd1c-c8ff-4f2e-a8d3-d547bd293b47" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_6e3a61ba-e60f-4e93-a2b7-5742dc386cb4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinanceLeaseLiabilitiesPaymentsDueAbstract_21eff9bf-863e-4251-80e9-e49a7a61a4dc" xlink:to="loc_us-gaap_FinanceLeaseLiabilityPaymentsDue_6e3a61ba-e60f-4e93-a2b7-5742dc386cb4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount_a54807f5-c5f7-45f9-9ddc-f5d35faf5cf1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinanceLeaseLiabilitiesPaymentsDueAbstract_21eff9bf-863e-4251-80e9-e49a7a61a4dc" xlink:to="loc_us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount_a54807f5-c5f7-45f9-9ddc-f5d35faf5cf1" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeaseLiability_608a23af-5c57-4302-bc94-90dee404197b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinanceLeaseLiabilitiesPaymentsDueAbstract_21eff9bf-863e-4251-80e9-e49a7a61a4dc" xlink:to="loc_us-gaap_FinanceLeaseLiability_608a23af-5c57-4302-bc94-90dee404197b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_LesseeOperatingLeaseLiabilityOptionToExtend_2046c80d-8c7c-4c3a-9953-524563220167" xlink:href="fi-20251231.xsd#fi_LesseeOperatingLeaseLiabilityOptionToExtend"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_18f28981-aa97-46b9-83fc-2b32923fb6e8" xlink:to="loc_fi_LesseeOperatingLeaseLiabilityOptionToExtend_2046c80d-8c7c-4c3a-9953-524563220167" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_LesseeOperatingLeaseLeaseNotYetCommencedLiabilityToBePaid_019c28fb-007a-7111-b90f-dcb5cbc1d2ba" xlink:href="fi-20251231.xsd#fi_LesseeOperatingLeaseLeaseNotYetCommencedLiabilityToBePaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_18f28981-aa97-46b9-83fc-2b32923fb6e8" xlink:to="loc_fi_LesseeOperatingLeaseLeaseNotYetCommencedLiabilityToBePaid_019c28fb-007a-7111-b90f-dcb5cbc1d2ba" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1_019c28fb-007a-7ab0-8589-f8183b4cd7b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_18f28981-aa97-46b9-83fc-2b32923fb6e8" xlink:to="loc_us-gaap_LesseeOperatingLeaseLeaseNotYetCommencedTermOfContract1_019c28fb-007a-7ab0-8589-f8183b4cd7b9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_LesseeFinanceLeaseLeaseNotYetCommencedLiabilityToBePaid_71418dd1-be3d-4184-9104-0e8732713203" xlink:href="fi-20251231.xsd#fi_LesseeFinanceLeaseLeaseNotYetCommencedLiabilityToBePaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_18f28981-aa97-46b9-83fc-2b32923fb6e8" xlink:to="loc_fi_LesseeFinanceLeaseLeaseNotYetCommencedLiabilityToBePaid_71418dd1-be3d-4184-9104-0e8732713203" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeFinanceLeaseLeaseNotYetCommencedTermOfContract1_ddacf997-2d65-47fc-b98a-40e4172a2caf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeFinanceLeaseLeaseNotYetCommencedTermOfContract1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_18f28981-aa97-46b9-83fc-2b32923fb6e8" xlink:to="loc_us-gaap_LesseeFinanceLeaseLeaseNotYetCommencedTermOfContract1_ddacf997-2d65-47fc-b98a-40e4172a2caf" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/LeasesComponentsofLeaseIncomeDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#LeasesComponentsofLeaseIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/LeasesComponentsofLeaseIncomeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LessorLeaseDescriptionLineItems_274f0b76-6d10-424a-b59b-d4649a65754c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LessorLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LessorLeaseDescriptionTable_7a0ffb4f-7b67-4a09-9f16-6ad5ccd9f8a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LessorLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_274f0b76-6d10-424a-b59b-d4649a65754c" xlink:to="loc_us-gaap_LessorLeaseDescriptionTable_7a0ffb4f-7b67-4a09-9f16-6ad5ccd9f8a0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_040beb5d-dd63-4f70-9d84-24d81404254e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LessorLeaseDescriptionTable_7a0ffb4f-7b67-4a09-9f16-6ad5ccd9f8a0" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_040beb5d-dd63-4f70-9d84-24d81404254e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_040beb5d-dd63-4f70-9d84-24d81404254e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_040beb5d-dd63-4f70-9d84-24d81404254e" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_040beb5d-dd63-4f70-9d84-24d81404254e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_c6a05d39-1e00-4333-80e6-6b161acc2112" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_040beb5d-dd63-4f70-9d84-24d81404254e" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_c6a05d39-1e00-4333-80e6-6b161acc2112" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesMember_5676a150-a01f-410f-8a74-4eefb3d1f101" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_c6a05d39-1e00-4333-80e6-6b161acc2112" xlink:to="loc_us-gaap_SalesMember_5676a150-a01f-410f-8a74-4eefb3d1f101" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_1841f2c2-311c-42a0-8ac9-31bb12a81f5f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_c6a05d39-1e00-4333-80e6-6b161acc2112" xlink:to="loc_us-gaap_CostOfSalesMember_1841f2c2-311c-42a0-8ac9-31bb12a81f5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss_dcf62af9-cd73-46f0-8bfd-cab3f4dad901" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_274f0b76-6d10-424a-b59b-d4649a65754c" xlink:to="loc_us-gaap_SalesTypeAndDirectFinancingLeasesProfitLoss_dcf62af9-cd73-46f0-8bfd-cab3f4dad901" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesTypeAndDirectFinancingLeasesInterestIncome_daec1d61-62c0-49d7-91d8-a54047db35f5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SalesTypeAndDirectFinancingLeasesInterestIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_274f0b76-6d10-424a-b59b-d4649a65754c" xlink:to="loc_us-gaap_SalesTypeAndDirectFinancingLeasesInterestIncome_daec1d61-62c0-49d7-91d8-a54047db35f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLeaseIncome_8c5ab118-70be-4980-9793-a6a0ac3f0b0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseLeaseIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_274f0b76-6d10-424a-b59b-d4649a65754c" xlink:to="loc_us-gaap_OperatingLeaseLeaseIncome_8c5ab118-70be-4980-9793-a6a0ac3f0b0b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseIncomeComprehensiveIncomeExtensibleList_4588c9a0-0deb-4763-8d9d-04e74f2a1c3a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLeaseIncomeComprehensiveIncomeExtensibleList"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LessorLeaseDescriptionLineItems_274f0b76-6d10-424a-b59b-d4649a65754c" xlink:to="loc_us-gaap_OperatingLeaseIncomeComprehensiveIncomeExtensibleList_4588c9a0-0deb-4763-8d9d-04e74f2a1c3a" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/DebtScheduleofDebtDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#DebtScheduleofDebtDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/DebtScheduleofDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_d23859f7-39f8-49d7-988c-bc94c3f81764" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_0e17fa9b-cf02-457e-ac30-7d5f0a5c152c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_d23859f7-39f8-49d7-988c-bc94c3f81764" xlink:to="loc_us-gaap_DebtInstrumentTable_0e17fa9b-cf02-457e-ac30-7d5f0a5c152c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_d6d0c283-6926-4cae-8aa8-54e87e5eae82" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0e17fa9b-cf02-457e-ac30-7d5f0a5c152c" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_d6d0c283-6926-4cae-8aa8-54e87e5eae82" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_d6d0c283-6926-4cae-8aa8-54e87e5eae82_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_d6d0c283-6926-4cae-8aa8-54e87e5eae82" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_d6d0c283-6926-4cae-8aa8-54e87e5eae82_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_c7d3c6f7-80d9-4ad8-a8fb-eda0bf4a4b89" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_d6d0c283-6926-4cae-8aa8-54e87e5eae82" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_c7d3c6f7-80d9-4ad8-a8fb-eda0bf4a4b89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignLineOfCreditMember_4facd3de-a76e-40ac-bd3f-1089865f1d80" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignLineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_c7d3c6f7-80d9-4ad8-a8fb-eda0bf4a4b89" xlink:to="loc_us-gaap_ForeignLineOfCreditMember_4facd3de-a76e-40ac-bd3f-1089865f1d80" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_dad53813-b719-4b76-a8ed-1b6073b94724" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0e17fa9b-cf02-457e-ac30-7d5f0a5c152c" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_dad53813-b719-4b76-a8ed-1b6073b94724" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_dad53813-b719-4b76-a8ed-1b6073b94724_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_dad53813-b719-4b76-a8ed-1b6073b94724" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_dad53813-b719-4b76-a8ed-1b6073b94724_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_3ca82a15-8573-4b8a-8621-9b93d576f9a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_dad53813-b719-4b76-a8ed-1b6073b94724" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_3ca82a15-8573-4b8a-8621-9b93d576f9a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_e96fc4e3-9e5f-401c-a76c-6b94b05cb249" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_3ca82a15-8573-4b8a-8621-9b93d576f9a0" xlink:to="loc_us-gaap_SeniorNotesMember_e96fc4e3-9e5f-401c-a76c-6b94b05cb249" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperMember_c8bd713c-6ece-4ad4-a153-219062ce2cf8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPaperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_3ca82a15-8573-4b8a-8621-9b93d576f9a0" xlink:to="loc_us-gaap_CommercialPaperMember_c8bd713c-6ece-4ad4-a153-219062ce2cf8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_49f2b61d-fa25-4a9a-92f5-00e604397d9a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_3ca82a15-8573-4b8a-8621-9b93d576f9a0" xlink:to="loc_us-gaap_LineOfCreditMember_49f2b61d-fa25-4a9a-92f5-00e604397d9a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_23dabc72-b2ef-4df7-ad38-46b64f203b8f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0e17fa9b-cf02-457e-ac30-7d5f0a5c152c" xlink:to="loc_us-gaap_CreditFacilityAxis_23dabc72-b2ef-4df7-ad38-46b64f203b8f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_23dabc72-b2ef-4df7-ad38-46b64f203b8f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_23dabc72-b2ef-4df7-ad38-46b64f203b8f" xlink:to="loc_us-gaap_CreditFacilityDomain_23dabc72-b2ef-4df7-ad38-46b64f203b8f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_5f554638-4767-499a-945f-2ab98b961624" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_23dabc72-b2ef-4df7-ad38-46b64f203b8f" xlink:to="loc_us-gaap_CreditFacilityDomain_5f554638-4767-499a-945f-2ab98b961624" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_fa24e2a9-fc6d-4782-a355-dcfb444b0303" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5f554638-4767-499a-945f-2ab98b961624" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_fa24e2a9-fc6d-4782-a355-dcfb444b0303" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_1dbdfb04-c166-488d-868c-d2213ce741e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_0e17fa9b-cf02-457e-ac30-7d5f0a5c152c" xlink:to="loc_us-gaap_DebtInstrumentAxis_1dbdfb04-c166-488d-868c-d2213ce741e7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_1dbdfb04-c166-488d-868c-d2213ce741e7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_1dbdfb04-c166-488d-868c-d2213ce741e7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_1dbdfb04-c166-488d-868c-d2213ce741e7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_1dbdfb04-c166-488d-868c-d2213ce741e7" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A3.85SeniorNotesDue2025Member_fac2123d-224d-4c03-b001-52889020f135" xlink:href="fi-20251231.xsd#fi_A3.85SeniorNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A3.85SeniorNotesDue2025Member_fac2123d-224d-4c03-b001-52889020f135" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A2.25SeniorNotesDueJuly2025Member_42297f66-073c-47e6-80a8-d4a378da0e2b" xlink:href="fi-20251231.xsd#fi_A2.25SeniorNotesDueJuly2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A2.25SeniorNotesDueJuly2025Member_42297f66-073c-47e6-80a8-d4a378da0e2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A3.2SeniorNotesDueJuly2026Member_cae0ec35-1a33-45ec-b31b-c973c22c1c44" xlink:href="fi-20251231.xsd#fi_A3.2SeniorNotesDueJuly2026Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A3.2SeniorNotesDueJuly2026Member_cae0ec35-1a33-45ec-b31b-c973c22c1c44" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A5.15SeniorNotesDueMarch2027Member_1aa0926d-8df1-48eb-9b46-b8508ddc7021" xlink:href="fi-20251231.xsd#fi_A5.15SeniorNotesDueMarch2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A5.15SeniorNotesDueMarch2027Member_1aa0926d-8df1-48eb-9b46-b8508ddc7021" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A2.25SeniorNotesDue2027Member_9c4c1de9-09da-4aca-97c1-56be91c614fa" xlink:href="fi-20251231.xsd#fi_A2.25SeniorNotesDue2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A2.25SeniorNotesDue2027Member_9c4c1de9-09da-4aca-97c1-56be91c614fa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A1.125SeniorNotesDueJuly2027Member_37474449-cd08-45e5-84ab-60c839be538b" xlink:href="fi-20251231.xsd#fi_A1.125SeniorNotesDueJuly2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A1.125SeniorNotesDueJuly2027Member_37474449-cd08-45e5-84ab-60c839be538b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A545SeniorNotesDueMarch2028Member_0f20af8b-d7e8-4eae-8337-4ef43cedfa68" xlink:href="fi-20251231.xsd#fi_A545SeniorNotesDueMarch2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A545SeniorNotesDueMarch2028Member_0f20af8b-d7e8-4eae-8337-4ef43cedfa68" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A2.875SeniorNotesDueJune2028Member_1be0845a-95d3-40ac-8fd3-941c7502ef1d" xlink:href="fi-20251231.xsd#fi_A2.875SeniorNotesDueJune2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A2.875SeniorNotesDueJune2028Member_1be0845a-95d3-40ac-8fd3-941c7502ef1d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A5375SeniorNotesDueAugust2028Member_901f1679-b5dd-481e-93dd-524ad7d1aa60" xlink:href="fi-20251231.xsd#fi_A5375SeniorNotesDueAugust2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A5375SeniorNotesDueAugust2028Member_901f1679-b5dd-481e-93dd-524ad7d1aa60" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A4.2SeniorNotesDueOctober2028Member_c8f06829-0225-47e9-b150-07055d2f1d9b" xlink:href="fi-20251231.xsd#fi_A4.2SeniorNotesDueOctober2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A4.2SeniorNotesDueOctober2028Member_c8f06829-0225-47e9-b150-07055d2f1d9b" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A3.5SeniorNotesDueJuly2029Member_d30dea4c-863f-4f3c-aea1-a4738c70029d" xlink:href="fi-20251231.xsd#fi_A3.5SeniorNotesDueJuly2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A3.5SeniorNotesDueJuly2029Member_d30dea4c-863f-4f3c-aea1-a4738c70029d" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A4.75SeniorNotesDueMarch2030Member_ddb621f6-4041-40b2-aaea-82022e14436c" xlink:href="fi-20251231.xsd#fi_A4.75SeniorNotesDueMarch2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A4.75SeniorNotesDueMarch2030Member_ddb621f6-4041-40b2-aaea-82022e14436c" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A2.65SeniorNotesDueJune2030Member_6b0b7a3d-efc5-4f05-a22f-feb22fe396d4" xlink:href="fi-20251231.xsd#fi_A2.65SeniorNotesDueJune2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A2.65SeniorNotesDueJune2030Member_6b0b7a3d-efc5-4f05-a22f-feb22fe396d4" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A1.625SeniorNotesDueJuly2030Member_34769ae2-79b3-4721-80d5-2c5daa6c71ba" xlink:href="fi-20251231.xsd#fi_A1.625SeniorNotesDueJuly2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A1.625SeniorNotesDueJuly2030Member_34769ae2-79b3-4721-80d5-2c5daa6c71ba" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A4.500SeniorNotesDueFebruary2031Member_04f9b3ad-397f-4d4a-8c3d-f7a136539de4" xlink:href="fi-20251231.xsd#fi_A4.500SeniorNotesDueFebruary2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A4.500SeniorNotesDueFebruary2031Member_04f9b3ad-397f-4d4a-8c3d-f7a136539de4" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A5.35SeniorNotesDueMarch2031Member_263ce2e2-c7aa-4c3a-ab62-72e09894a39b" xlink:href="fi-20251231.xsd#fi_A5.35SeniorNotesDueMarch2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A5.35SeniorNotesDueMarch2031Member_263ce2e2-c7aa-4c3a-ab62-72e09894a39b" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A4500SeniorNotesDueMay2031Member_25eee8c2-d30a-4668-8f74-2e7e30e3c993" xlink:href="fi-20251231.xsd#fi_A4500SeniorNotesDueMay2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A4500SeniorNotesDueMay2031Member_25eee8c2-d30a-4668-8f74-2e7e30e3c993" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A3.0SeniorNotesDueJuly2031Member_b0f25680-dece-4a52-8f72-de69b70a65d5" xlink:href="fi-20251231.xsd#fi_A3.0SeniorNotesDueJuly2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A3.0SeniorNotesDueJuly2031Member_b0f25680-dece-4a52-8f72-de69b70a65d5" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A3.500SeniorNotesDueJune2032Member_0a598156-04f2-4d31-93a2-d72ac5bb3512" xlink:href="fi-20251231.xsd#fi_A3.500SeniorNotesDueJune2032Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A3.500SeniorNotesDueJune2032Member_0a598156-04f2-4d31-93a2-d72ac5bb3512" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A56SeniorNotesDueMarch2033Member_1e487680-9514-4a80-8a46-9b890fb9c65d" xlink:href="fi-20251231.xsd#fi_A56SeniorNotesDueMarch2033Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A56SeniorNotesDueMarch2033Member_1e487680-9514-4a80-8a46-9b890fb9c65d" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A5625SeniorNotesDueAugust2033Member_735a0ae8-3f25-48b2-af3e-8f208dd09d9d" xlink:href="fi-20251231.xsd#fi_A5625SeniorNotesDueAugust2033Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A5625SeniorNotesDueAugust2033Member_735a0ae8-3f25-48b2-af3e-8f208dd09d9d" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A5.45SeniorNotesDueMarch2034Member_80b9c032-1c98-48d2-8615-9780f4801132" xlink:href="fi-20251231.xsd#fi_A5.45SeniorNotesDueMarch2034Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A5.45SeniorNotesDueMarch2034Member_80b9c032-1c98-48d2-8615-9780f4801132" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A5.15SeniorNotesDueAugust2034Member_5791b0a5-ac56-4086-9f3e-a40107201280" xlink:href="fi-20251231.xsd#fi_A5.15SeniorNotesDueAugust2034Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A5.15SeniorNotesDueAugust2034Member_5791b0a5-ac56-4086-9f3e-a40107201280" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A5.250SeniorNotesDueAugust2035Member_d637ca93-9c5d-42fc-930e-1e9c378dc060" xlink:href="fi-20251231.xsd#fi_A5.250SeniorNotesDueAugust2035Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A5.250SeniorNotesDueAugust2035Member_d637ca93-9c5d-42fc-930e-1e9c378dc060" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A4.000SeniorNotesDueJune2036Member_1b7ff2b3-19a9-4cfd-9f66-afe6ff9af64e" xlink:href="fi-20251231.xsd#fi_A4.000SeniorNotesDueJune2036Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A4.000SeniorNotesDueJune2036Member_1b7ff2b3-19a9-4cfd-9f66-afe6ff9af64e" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A4.4SeniorNotesDueJuly2049Member_1549d891-7269-4e60-bdef-adef0cf934c2" xlink:href="fi-20251231.xsd#fi_A4.4SeniorNotesDueJuly2049Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_A4.4SeniorNotesDueJuly2049Member_1549d891-7269-4e60-bdef-adef0cf934c2" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_USUnsecuredCommercialPaperNotesMember_930cc8d1-b983-4086-b840-d72cb17c55dd" xlink:href="fi-20251231.xsd#fi_USUnsecuredCommercialPaperNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_USUnsecuredCommercialPaperNotesMember_930cc8d1-b983-4086-b840-d72cb17c55dd" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_EuroUnsecuredCommercialPaperNotesMember_1d58724e-de94-4663-9f84-427ae30c9678" xlink:href="fi-20251231.xsd#fi_EuroUnsecuredCommercialPaperNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_6aacc5ac-5a1b-46e4-a949-4a01fa0aaf7e" xlink:to="loc_fi_EuroUnsecuredCommercialPaperNotesMember_1d58724e-de94-4663-9f84-427ae30c9678" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_abbd43d3-2e9c-49d1-b3d0-401e90b08231" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_d23859f7-39f8-49d7-988c-bc94c3f81764" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_abbd43d3-2e9c-49d1-b3d0-401e90b08231" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtCurrentAbstract_435838a5-845a-4666-bf06-1f39f2ffdcdc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_d23859f7-39f8-49d7-988c-bc94c3f81764" xlink:to="loc_us-gaap_DebtCurrentAbstract_435838a5-845a-4666-bf06-1f39f2ffdcdc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtCurrent_90a34fea-1d3d-4e9d-b955-fd18787ebe30" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtCurrentAbstract_435838a5-845a-4666-bf06-1f39f2ffdcdc" xlink:to="loc_us-gaap_DebtCurrent_90a34fea-1d3d-4e9d-b955-fd18787ebe30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_FinanceLeaseLiabilityAndOtherCurrent_1ff8860d-650d-43cf-9978-c3aada913a00" xlink:href="fi-20251231.xsd#fi_FinanceLeaseLiabilityAndOtherCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtCurrentAbstract_435838a5-845a-4666-bf06-1f39f2ffdcdc" xlink:to="loc_fi_FinanceLeaseLiabilityAndOtherCurrent_1ff8860d-650d-43cf-9978-c3aada913a00" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtOtherDisclosuresAbstract_668e0d94-5bd9-4191-9245-3d928ff8ccef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtOtherDisclosuresAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_d23859f7-39f8-49d7-988c-bc94c3f81764" xlink:to="loc_us-gaap_LongTermDebtOtherDisclosuresAbstract_668e0d94-5bd9-4191-9245-3d928ff8ccef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_966377c3-bb63-49c4-8e25-8f534e0888e5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtOtherDisclosuresAbstract_668e0d94-5bd9-4191-9245-3d928ff8ccef" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_966377c3-bb63-49c4-8e25-8f534e0888e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_f2d13d4d-611d-4c62-a56e-f8ec9bb755a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtOtherDisclosuresAbstract_668e0d94-5bd9-4191-9245-3d928ff8ccef" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_f2d13d4d-611d-4c62-a56e-f8ec9bb755a6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_FinanceLeaseLiabilityAndOtherNoncurrent_799a8dfe-1b3d-4cc9-9b15-7eba2bbfc54f" xlink:href="fi-20251231.xsd#fi_FinanceLeaseLiabilityAndOtherNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtOtherDisclosuresAbstract_668e0d94-5bd9-4191-9245-3d928ff8ccef" xlink:to="loc_fi_FinanceLeaseLiabilityAndOtherNoncurrent_799a8dfe-1b3d-4cc9-9b15-7eba2bbfc54f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_cad6b826-a971-4e04-a5b3-8f0d7f0f9502" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtOtherDisclosuresAbstract_668e0d94-5bd9-4191-9245-3d928ff8ccef" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligations_cad6b826-a971-4e04-a5b3-8f0d7f0f9502" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/DebtNarrativeDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#DebtNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/DebtNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_aa725859-c84f-43bc-ab65-8a7e05fedafc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_8b4c7756-6fc8-42ca-873f-b1b47eacd5d9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aa725859-c84f-43bc-ab65-8a7e05fedafc" xlink:to="loc_us-gaap_DebtInstrumentTable_8b4c7756-6fc8-42ca-873f-b1b47eacd5d9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_db7d297f-5b4c-4be4-b22d-9a91dbc64ce9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8b4c7756-6fc8-42ca-873f-b1b47eacd5d9" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_db7d297f-5b4c-4be4-b22d-9a91dbc64ce9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_db7d297f-5b4c-4be4-b22d-9a91dbc64ce9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_db7d297f-5b4c-4be4-b22d-9a91dbc64ce9" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_db7d297f-5b4c-4be4-b22d-9a91dbc64ce9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_f0cf6d0e-cfdd-4beb-8222-1f42e5f5624a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_db7d297f-5b4c-4be4-b22d-9a91dbc64ce9" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_f0cf6d0e-cfdd-4beb-8222-1f42e5f5624a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_d4e3eb44-2d77-41f1-abbf-37e35d92f3c3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_f0cf6d0e-cfdd-4beb-8222-1f42e5f5624a" xlink:to="loc_us-gaap_SeniorNotesMember_d4e3eb44-2d77-41f1-abbf-37e35d92f3c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommercialPaperMember_0189b31d-1ba6-492d-bc1c-e91e547a65b2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPaperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_f0cf6d0e-cfdd-4beb-8222-1f42e5f5624a" xlink:to="loc_us-gaap_CommercialPaperMember_0189b31d-1ba6-492d-bc1c-e91e547a65b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_66849d80-0ba9-4eb8-aff3-97906ec14c9b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_f0cf6d0e-cfdd-4beb-8222-1f42e5f5624a" xlink:to="loc_us-gaap_LineOfCreditMember_66849d80-0ba9-4eb8-aff3-97906ec14c9b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_LoansPayableAndSeniorNotesMember_f09f2f5d-0900-4cfe-bef5-baca3d382287" xlink:href="fi-20251231.xsd#fi_LoansPayableAndSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_f0cf6d0e-cfdd-4beb-8222-1f42e5f5624a" xlink:to="loc_fi_LoansPayableAndSeniorNotesMember_f09f2f5d-0900-4cfe-bef5-baca3d382287" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_82b4b847-915d-410b-b9a6-dfa5a5e9ff87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8b4c7756-6fc8-42ca-873f-b1b47eacd5d9" xlink:to="loc_us-gaap_CreditFacilityAxis_82b4b847-915d-410b-b9a6-dfa5a5e9ff87" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_82b4b847-915d-410b-b9a6-dfa5a5e9ff87_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_82b4b847-915d-410b-b9a6-dfa5a5e9ff87" xlink:to="loc_us-gaap_CreditFacilityDomain_82b4b847-915d-410b-b9a6-dfa5a5e9ff87_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_60b8e719-66e4-4407-ace0-7b65cc0b4b62" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_82b4b847-915d-410b-b9a6-dfa5a5e9ff87" xlink:to="loc_us-gaap_CreditFacilityDomain_60b8e719-66e4-4407-ace0-7b65cc0b4b62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_9f3f44ea-356e-490f-aaaa-146b9e05fc87" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_60b8e719-66e4-4407-ace0-7b65cc0b4b62" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_9f3f44ea-356e-490f-aaaa-146b9e05fc87" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_341927f9-04af-49a4-9fe2-b8a934bf6ead" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8b4c7756-6fc8-42ca-873f-b1b47eacd5d9" xlink:to="loc_us-gaap_DebtInstrumentAxis_341927f9-04af-49a4-9fe2-b8a934bf6ead" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_341927f9-04af-49a4-9fe2-b8a934bf6ead_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_341927f9-04af-49a4-9fe2-b8a934bf6ead" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_341927f9-04af-49a4-9fe2-b8a934bf6ead_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_341927f9-04af-49a4-9fe2-b8a934bf6ead" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A4.550SeniorNotesDueFebruary2031Member_f3a54a28-eb49-46cd-b64a-779e57dc86d5" xlink:href="fi-20251231.xsd#fi_A4.550SeniorNotesDueFebruary2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_A4.550SeniorNotesDueFebruary2031Member_f3a54a28-eb49-46cd-b64a-779e57dc86d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A5.250SeniorNotesDueAugust2035Member_1d496312-ee11-43a7-b88c-17395772a4eb" xlink:href="fi-20251231.xsd#fi_A5.250SeniorNotesDueAugust2035Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_A5.250SeniorNotesDueAugust2035Member_1d496312-ee11-43a7-b88c-17395772a4eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A2.875SeniorNotesDueJune2028Member_88757a3b-959e-4b6a-87a0-ad789af149a2" xlink:href="fi-20251231.xsd#fi_A2.875SeniorNotesDueJune2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_A2.875SeniorNotesDueJune2028Member_88757a3b-959e-4b6a-87a0-ad789af149a2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A3.5SeniorNotesDueJune2032Member_4fc7da6d-fb59-479f-af83-d6154120334d" xlink:href="fi-20251231.xsd#fi_A3.5SeniorNotesDueJune2032Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_A3.5SeniorNotesDueJune2032Member_4fc7da6d-fb59-479f-af83-d6154120334d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A4.0SeniorNotesDueJune2036Member_eeba44ba-5801-4405-a740-6ce4c981a5ed" xlink:href="fi-20251231.xsd#fi_A4.0SeniorNotesDueJune2036Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_A4.0SeniorNotesDueJune2036Member_eeba44ba-5801-4405-a740-6ce4c981a5ed" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A3.85SeniorNotesDue2025Member_691dac2c-c627-42a8-99a0-c8f7914da9f5" xlink:href="fi-20251231.xsd#fi_A3.85SeniorNotesDue2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_A3.85SeniorNotesDue2025Member_691dac2c-c627-42a8-99a0-c8f7914da9f5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A2.25SeniorNotesDueJuly2025Member_f8cdb260-94df-45bd-b3a3-be6a2955d75c" xlink:href="fi-20251231.xsd#fi_A2.25SeniorNotesDueJuly2025Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_A2.25SeniorNotesDueJuly2025Member_f8cdb260-94df-45bd-b3a3-be6a2955d75c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A4.75SeniorNotesDueMarch2030Member_019bb28d-3c7e-7727-b5dd-67c891fe618b" xlink:href="fi-20251231.xsd#fi_A4.75SeniorNotesDueMarch2030Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_A4.75SeniorNotesDueMarch2030Member_019bb28d-3c7e-7727-b5dd-67c891fe618b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A5.15SeniorNotesDueAugust2034Member_019bb28d-3c7e-75a1-a123-d19902fef45d" xlink:href="fi-20251231.xsd#fi_A5.15SeniorNotesDueAugust2034Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_A5.15SeniorNotesDueAugust2034Member_019bb28d-3c7e-75a1-a123-d19902fef45d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A5.150SeniorNotesDueMarch2027Member_019bb28d-3c7e-71f8-83e5-96c0fcd2f3a6" xlink:href="fi-20251231.xsd#fi_A5.150SeniorNotesDueMarch2027Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_A5.150SeniorNotesDueMarch2027Member_019bb28d-3c7e-71f8-83e5-96c0fcd2f3a6" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A5.350SeniorNotesDueMarch2031Member_019bb28d-3c7e-73ea-9ed3-4a0bd4938967" xlink:href="fi-20251231.xsd#fi_A5.350SeniorNotesDueMarch2031Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_A5.350SeniorNotesDueMarch2031Member_019bb28d-3c7e-73ea-9ed3-4a0bd4938967" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A5.450SeniorNotesDueMarch2034Member_019bb28d-3c7e-7291-bdd6-01ae9d4da7b1" xlink:href="fi-20251231.xsd#fi_A5.450SeniorNotesDueMarch2034Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_A5.450SeniorNotesDueMarch2034Member_019bb28d-3c7e-7291-bdd6-01ae9d4da7b1" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_A2.75SeniorNotesDueJuly2024Member_019bb28d-3c7e-7ec5-98a7-fddd40a684d2" xlink:href="fi-20251231.xsd#fi_A2.75SeniorNotesDueJuly2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_A2.75SeniorNotesDueJuly2024Member_019bb28d-3c7e-7ec5-98a7-fddd40a684d2" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_USUnsecuredCommercialPaperNotesMember_7720a53d-f0e3-4573-bc1e-0feacfa70c5b" xlink:href="fi-20251231.xsd#fi_USUnsecuredCommercialPaperNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_USUnsecuredCommercialPaperNotesMember_7720a53d-f0e3-4573-bc1e-0feacfa70c5b" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_EuroUnsecuredCommercialPaperNotesMember_85d087da-b592-4258-b9c6-2b76c69ecbc2" xlink:href="fi-20251231.xsd#fi_EuroUnsecuredCommercialPaperNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_764f7cf6-6f49-4200-90b6-fe3225a280a2" xlink:to="loc_fi_EuroUnsecuredCommercialPaperNotesMember_85d087da-b592-4258-b9c6-2b76c69ecbc2" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_30bf2fbc-6ff0-4be0-8faa-cc10a6cbe9fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8b4c7756-6fc8-42ca-873f-b1b47eacd5d9" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_30bf2fbc-6ff0-4be0-8faa-cc10a6cbe9fc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_30bf2fbc-6ff0-4be0-8faa-cc10a6cbe9fc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_30bf2fbc-6ff0-4be0-8faa-cc10a6cbe9fc" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_30bf2fbc-6ff0-4be0-8faa-cc10a6cbe9fc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_e9004ff0-46cc-47db-9814-a7c36482a5e2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_30bf2fbc-6ff0-4be0-8faa-cc10a6cbe9fc" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_e9004ff0-46cc-47db-9814-a7c36482a5e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_cd98f2f3-3d11-44ce-86ec-466e87420762" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_e9004ff0-46cc-47db-9814-a7c36482a5e2" xlink:to="loc_us-gaap_LineOfCreditMember_cd98f2f3-3d11-44ce-86ec-466e87420762" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignLineOfCreditMember_1b9410e4-0350-4981-b864-f03a763dfe3b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignLineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_e9004ff0-46cc-47db-9814-a7c36482a5e2" xlink:to="loc_us-gaap_ForeignLineOfCreditMember_1b9410e4-0350-4981-b864-f03a763dfe3b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_64a09780-32c3-44ed-ac5d-96a6f6dba873" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_8b4c7756-6fc8-42ca-873f-b1b47eacd5d9" xlink:to="loc_dei_LegalEntityAxis_64a09780-32c3-44ed-ac5d-96a6f6dba873" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_64a09780-32c3-44ed-ac5d-96a6f6dba873_default" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_64a09780-32c3-44ed-ac5d-96a6f6dba873" xlink:to="loc_dei_EntityDomain_64a09780-32c3-44ed-ac5d-96a6f6dba873_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_360091b5-cd8d-44e2-9fde-a810d1311e64" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_64a09780-32c3-44ed-ac5d-96a6f6dba873" xlink:to="loc_dei_EntityDomain_360091b5-cd8d-44e2-9fde-a810d1311e64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_FiservFundingUnlimitedCompanyMember_e5574545-87be-42c4-8613-df3ef42b8d01" xlink:href="fi-20251231.xsd#fi_FiservFundingUnlimitedCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_360091b5-cd8d-44e2-9fde-a810d1311e64" xlink:to="loc_fi_FiservFundingUnlimitedCompanyMember_e5574545-87be-42c4-8613-df3ef42b8d01" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_7a463ec6-88b7-4aef-97f3-b83bc6f3ec92" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aa725859-c84f-43bc-ab65-8a7e05fedafc" xlink:to="loc_us-gaap_LongTermDebt_7a463ec6-88b7-4aef-97f3-b83bc6f3ec92" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_DebtInstrumentInterestRateSubjectToIncreaseMaximum_df95dac6-cfaf-41d3-a816-cec79dfcb2a6" xlink:href="fi-20251231.xsd#fi_DebtInstrumentInterestRateSubjectToIncreaseMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aa725859-c84f-43bc-ab65-8a7e05fedafc" xlink:to="loc_fi_DebtInstrumentInterestRateSubjectToIncreaseMaximum_df95dac6-cfaf-41d3-a816-cec79dfcb2a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_70a8e778-2204-4998-9dcc-ff09a5072684" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aa725859-c84f-43bc-ab65-8a7e05fedafc" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_70a8e778-2204-4998-9dcc-ff09a5072684" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_ebc59070-d0e1-4668-992c-4324de4832ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aa725859-c84f-43bc-ab65-8a7e05fedafc" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_ebc59070-d0e1-4668-992c-4324de4832ef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_3c5bae83-84da-4750-a2b0-3b8021491985" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aa725859-c84f-43bc-ab65-8a7e05fedafc" xlink:to="loc_us-gaap_DebtInstrumentTerm_3c5bae83-84da-4750-a2b0-3b8021491985" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_05b74651-0afb-4f09-8858-6b75e317ef3d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aa725859-c84f-43bc-ab65-8a7e05fedafc" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_05b74651-0afb-4f09-8858-6b75e317ef3d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_139ea305-9238-496f-bc48-a771712f8873" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aa725859-c84f-43bc-ab65-8a7e05fedafc" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_139ea305-9238-496f-bc48-a771712f8873" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_4bd437df-ba4d-4789-be40-8ee0876e53e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aa725859-c84f-43bc-ab65-8a7e05fedafc" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_4bd437df-ba4d-4789-be40-8ee0876e53e0" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_DebtInstrumentCovenantDebtToEBITDARatio_7d5dd6d7-1469-42a2-ac97-4bc698a4f529" xlink:href="fi-20251231.xsd#fi_DebtInstrumentCovenantDebtToEBITDARatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aa725859-c84f-43bc-ab65-8a7e05fedafc" xlink:to="loc_fi_DebtInstrumentCovenantDebtToEBITDARatio_7d5dd6d7-1469-42a2-ac97-4bc698a4f529" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_93fd4473-2c9f-434f-ad59-5855df692c61" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aa725859-c84f-43bc-ab65-8a7e05fedafc" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_93fd4473-2c9f-434f-ad59-5855df692c61" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_80ede0aa-253a-4ec6-a0f2-b91168c31df3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aa725859-c84f-43bc-ab65-8a7e05fedafc" xlink:to="loc_us-gaap_LineOfCredit_80ede0aa-253a-4ec6-a0f2-b91168c31df3" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/DebtScheduleofForeignLinesofCreditbyCountryDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#DebtScheduleofForeignLinesofCreditbyCountryDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/DebtScheduleofForeignLinesofCreditbyCountryDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtLineItems_d7c08bf3-a24f-47f0-b149-9447781e2e46" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShortTermDebtTable_2d5b27dd-a84b-4433-951a-4c1c5780b5f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShortTermDebtTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShortTermDebtLineItems_d7c08bf3-a24f-47f0-b149-9447781e2e46" xlink:to="loc_us-gaap_ScheduleOfShortTermDebtTable_2d5b27dd-a84b-4433-951a-4c1c5780b5f7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_cc37afd1-e17f-4247-b8fe-cbc7e88d3a42" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShortTermDebtTable_2d5b27dd-a84b-4433-951a-4c1c5780b5f7" xlink:to="loc_srt_StatementGeographicalAxis_cc37afd1-e17f-4247-b8fe-cbc7e88d3a42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_cc37afd1-e17f-4247-b8fe-cbc7e88d3a42_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_cc37afd1-e17f-4247-b8fe-cbc7e88d3a42" xlink:to="loc_srt_SegmentGeographicalDomain_cc37afd1-e17f-4247-b8fe-cbc7e88d3a42_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_adcca985-541c-455e-bf2f-de586a95b678" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_cc37afd1-e17f-4247-b8fe-cbc7e88d3a42" xlink:to="loc_srt_SegmentGeographicalDomain_adcca985-541c-455e-bf2f-de586a95b678" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_AR_86290ca8-9d62-4e12-81b4-0442ab61f431" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_AR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_adcca985-541c-455e-bf2f-de586a95b678" xlink:to="loc_country_AR_86290ca8-9d62-4e12-81b4-0442ab61f431" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_BR_626c70eb-2fc3-4e25-9cc0-997abc2cf390" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_BR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_adcca985-541c-455e-bf2f-de586a95b678" xlink:to="loc_country_BR_626c70eb-2fc3-4e25-9cc0-997abc2cf390" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_OtherMember_aac2b5b4-969c-4092-bfa2-5c174015cd77" xlink:href="fi-20251231.xsd#fi_OtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_adcca985-541c-455e-bf2f-de586a95b678" xlink:to="loc_fi_OtherMember_aac2b5b4-969c-4092-bfa2-5c174015cd77" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_0f51c32a-4e06-4c2f-944a-e8779c8644e4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShortTermDebtTable_2d5b27dd-a84b-4433-951a-4c1c5780b5f7" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_0f51c32a-4e06-4c2f-944a-e8779c8644e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_0f51c32a-4e06-4c2f-944a-e8779c8644e4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_0f51c32a-4e06-4c2f-944a-e8779c8644e4" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_0f51c32a-4e06-4c2f-944a-e8779c8644e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_756050be-e602-4e64-ae15-06f2a9df1208" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_0f51c32a-4e06-4c2f-944a-e8779c8644e4" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_756050be-e602-4e64-ae15-06f2a9df1208" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignLineOfCreditMember_39bb8aee-ba92-46cb-a3f6-3ee2d06dff3d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignLineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_756050be-e602-4e64-ae15-06f2a9df1208" xlink:to="loc_us-gaap_ForeignLineOfCreditMember_39bb8aee-ba92-46cb-a3f6-3ee2d06dff3d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_49510b4d-fa47-4d39-8461-32daaa1519eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtLineItems_d7c08bf3-a24f-47f0-b149-9447781e2e46" xlink:to="loc_us-gaap_ShortTermBorrowings_49510b4d-fa47-4d39-8461-32daaa1519eb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_cca32d0d-3f16-4d60-884f-cb263ee75066" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtLineItems_d7c08bf3-a24f-47f0-b149-9447781e2e46" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_cca32d0d-3f16-4d60-884f-cb263ee75066" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/RedeemableNoncontrollingInterestsNarrativeDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#RedeemableNoncontrollingInterestsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/RedeemableNoncontrollingInterestsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestLineItems_efe68860-6b67-4d3c-8609-1d36906272e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterestLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestTable_d2d73905-1de2-419d-8394-5f5778a31487" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterestTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_efe68860-6b67-4d3c-8609-1d36906272e0" xlink:to="loc_us-gaap_MinorityInterestTable_d2d73905-1de2-419d-8394-5f5778a31487" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_93b0ddfb-00d0-482d-b596-c77f6b0e89af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_d2d73905-1de2-419d-8394-5f5778a31487" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_93b0ddfb-00d0-482d-b596-c77f6b0e89af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_93b0ddfb-00d0-482d-b596-c77f6b0e89af_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_93b0ddfb-00d0-482d-b596-c77f6b0e89af" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_93b0ddfb-00d0-482d-b596-c77f6b0e89af_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bcd4ce6a-7054-4ec1-88ee-c457122c85b9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_93b0ddfb-00d0-482d-b596-c77f6b0e89af" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bcd4ce6a-7054-4ec1-88ee-c457122c85b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_FirstDataMember_1052bdff-abb2-4117-b63a-31761c0fab89" xlink:href="fi-20251231.xsd#fi_FirstDataMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bcd4ce6a-7054-4ec1-88ee-c457122c85b9" xlink:to="loc_fi_FirstDataMember_1052bdff-abb2-4117-b63a-31761c0fab89" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_59a5a1e5-d498-41ff-88ee-971a81ee84d4" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_d2d73905-1de2-419d-8394-5f5778a31487" xlink:to="loc_srt_OwnershipAxis_59a5a1e5-d498-41ff-88ee-971a81ee84d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_59a5a1e5-d498-41ff-88ee-971a81ee84d4_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_59a5a1e5-d498-41ff-88ee-971a81ee84d4" xlink:to="loc_srt_OwnershipDomain_59a5a1e5-d498-41ff-88ee-971a81ee84d4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_5bb79405-e8fa-461d-b4b3-269860dffe76" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_59a5a1e5-d498-41ff-88ee-971a81ee84d4" xlink:to="loc_srt_OwnershipDomain_5bb79405-e8fa-461d-b4b3-269860dffe76" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_FirstDataJointVentureMember_89c16c9b-d932-420e-a9d0-c685af8c58d2" xlink:href="fi-20251231.xsd#fi_FirstDataJointVentureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_5bb79405-e8fa-461d-b4b3-269860dffe76" xlink:to="loc_fi_FirstDataJointVentureMember_89c16c9b-d932-420e-a9d0-c685af8c58d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_NumberOfRedeemableNoncontrollingInterests_b4307d3b-3125-4ca4-95c1-bca014f1462c" xlink:href="fi-20251231.xsd#fi_NumberOfRedeemableNoncontrollingInterests"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_efe68860-6b67-4d3c-8609-1d36906272e0" xlink:to="loc_fi_NumberOfRedeemableNoncontrollingInterests_b4307d3b-3125-4ca4-95c1-bca014f1462c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_0f021534-b389-4fa2-979c-dfda68c106b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_efe68860-6b67-4d3c-8609-1d36906272e0" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_0f021534-b389-4fa2-979c-dfda68c106b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestChangeInRedemptionValue_07ea742f-9ad7-4720-80cd-7f6591d5b6d3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterestChangeInRedemptionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_efe68860-6b67-4d3c-8609-1d36906272e0" xlink:to="loc_us-gaap_MinorityInterestChangeInRedemptionValue_07ea742f-9ad7-4720-80cd-7f6591d5b6d3" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/AccumulatedOtherComprehensiveLossScheduleofAccumulatedOtherComprehensiveLossDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#AccumulatedOtherComprehensiveLossScheduleofAccumulatedOtherComprehensiveLossDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/AccumulatedOtherComprehensiveLossScheduleofAccumulatedOtherComprehensiveLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_a0ced160-3338-413f-9dcb-a6b3216859e1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_77362587-4dcb-44cb-aaf6-2cc5642eecd4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_a0ced160-3338-413f-9dcb-a6b3216859e1" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_77362587-4dcb-44cb-aaf6-2cc5642eecd4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_b2e95261-365f-46a3-85ad-b6aca42a9cb5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_77362587-4dcb-44cb-aaf6-2cc5642eecd4" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_b2e95261-365f-46a3-85ad-b6aca42a9cb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_b2e95261-365f-46a3-85ad-b6aca42a9cb5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_b2e95261-365f-46a3-85ad-b6aca42a9cb5" xlink:to="loc_us-gaap_EquityComponentDomain_b2e95261-365f-46a3-85ad-b6aca42a9cb5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_d1dbdec6-2369-48fe-a667-0a0b80563159" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_b2e95261-365f-46a3-85ad-b6aca42a9cb5" xlink:to="loc_us-gaap_EquityComponentDomain_d1dbdec6-2369-48fe-a667-0a0b80563159" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_f74163ad-0e2e-431a-a141-d7d10a510852" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_d1dbdec6-2369-48fe-a667-0a0b80563159" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_f74163ad-0e2e-431a-a141-d7d10a510852" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_9c816090-361c-449e-9d76-d7a221b0bf1c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_f74163ad-0e2e-431a-a141-d7d10a510852" xlink:to="loc_us-gaap_AccumulatedGainLossNetCashFlowHedgeParentMember_9c816090-361c-449e-9d76-d7a221b0bf1c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_a90e0bc7-0aaf-4eb2-8acd-f191090aa11e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_f74163ad-0e2e-431a-a141-d7d10a510852" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_a90e0bc7-0aaf-4eb2-8acd-f191090aa11e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_ba7c5212-64ea-4c03-b42d-bf14b3a57a64" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_f74163ad-0e2e-431a-a141-d7d10a510852" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_ba7c5212-64ea-4c03-b42d-bf14b3a57a64" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_612b9da4-bd13-48b9-baff-cea64efa3741" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_a0ced160-3338-413f-9dcb-a6b3216859e1" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_612b9da4-bd13-48b9-baff-cea64efa3741" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_e33415a9-951b-4a34-bf63-6244cd294e96" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_612b9da4-bd13-48b9-baff-cea64efa3741" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_e33415a9-951b-4a34-bf63-6244cd294e96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_76c0b10d-99c7-46d3-ba5a-58ef5e955d84" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_612b9da4-bd13-48b9-baff-cea64efa3741" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_76c0b10d-99c7-46d3-ba5a-58ef5e955d84" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_ac2d1117-73c1-4549-84c5-dd7295311242" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_612b9da4-bd13-48b9-baff-cea64efa3741" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_ac2d1117-73c1-4549-84c5-dd7295311242" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_964bb93a-5584-47c5-8a04-8cb47cc078e3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTaxAbstract_612b9da4-bd13-48b9-baff-cea64efa3741" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_964bb93a-5584-47c5-8a04-8cb47cc078e3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_afee8e4b-e977-44f3-9c32-317b4f047ab0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/ShareBasedCompensationNarrativeDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#ShareBasedCompensationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/ShareBasedCompensationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4873e176-b716-45ac-a79f-835e237ae72c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_14d86411-1e2a-4773-a076-f18885295cbc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4873e176-b716-45ac-a79f-835e237ae72c" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_14d86411-1e2a-4773-a076-f18885295cbc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_cbb13e02-710e-4b70-825f-f1f5d2f0d289" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_14d86411-1e2a-4773-a076-f18885295cbc" xlink:to="loc_us-gaap_AwardTypeAxis_cbb13e02-710e-4b70-825f-f1f5d2f0d289" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cbb13e02-710e-4b70-825f-f1f5d2f0d289_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_cbb13e02-710e-4b70-825f-f1f5d2f0d289" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cbb13e02-710e-4b70-825f-f1f5d2f0d289_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f6b20bda-d9f2-4ed7-a619-f83726eba9eb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_cbb13e02-710e-4b70-825f-f1f5d2f0d289" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f6b20bda-d9f2-4ed7-a619-f83726eba9eb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_TimeBasedRestrictedStockUnitsRSUsMember_9803d3b9-b245-43bd-83d6-0106c89765a4" xlink:href="fi-20251231.xsd#fi_TimeBasedRestrictedStockUnitsRSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f6b20bda-d9f2-4ed7-a619-f83726eba9eb" xlink:to="loc_fi_TimeBasedRestrictedStockUnitsRSUsMember_9803d3b9-b245-43bd-83d6-0106c89765a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_bde03f5c-42dd-4fb4-bdfb-084c584c10f1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f6b20bda-d9f2-4ed7-a619-f83726eba9eb" xlink:to="loc_us-gaap_PerformanceSharesMember_bde03f5c-42dd-4fb4-bdfb-084c584c10f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_9c46437d-adfa-4cf6-a9d1-a520d3921e15" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f6b20bda-d9f2-4ed7-a619-f83726eba9eb" xlink:to="loc_us-gaap_EmployeeStockOptionMember_9c46437d-adfa-4cf6-a9d1-a520d3921e15" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockMember_3503af4f-eefc-4c17-b565-18f6155abad9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f6b20bda-d9f2-4ed7-a619-f83726eba9eb" xlink:to="loc_us-gaap_EmployeeStockMember_3503af4f-eefc-4c17-b565-18f6155abad9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_RestrictedStockUnitsAndRestrictedStockAwardsMember_019be6aa-4e0a-7a32-98a5-3b5097d2b989" xlink:href="fi-20251231.xsd#fi_RestrictedStockUnitsAndRestrictedStockAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_f6b20bda-d9f2-4ed7-a619-f83726eba9eb" xlink:to="loc_fi_RestrictedStockUnitsAndRestrictedStockAwardsMember_019be6aa-4e0a-7a32-98a5-3b5097d2b989" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_3cce1a39-6c05-47bc-b7d5-a135c7449929" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_14d86411-1e2a-4773-a076-f18885295cbc" xlink:to="loc_srt_RangeAxis_3cce1a39-6c05-47bc-b7d5-a135c7449929" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_3cce1a39-6c05-47bc-b7d5-a135c7449929_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_3cce1a39-6c05-47bc-b7d5-a135c7449929" xlink:to="loc_srt_RangeMember_3cce1a39-6c05-47bc-b7d5-a135c7449929_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_850c923c-e1b4-4981-b349-0ee558d3e3a8" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_3cce1a39-6c05-47bc-b7d5-a135c7449929" xlink:to="loc_srt_RangeMember_850c923c-e1b4-4981-b349-0ee558d3e3a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_0d4c7ffd-ab28-4323-9395-2364a0d22f43" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_850c923c-e1b4-4981-b349-0ee558d3e3a8" xlink:to="loc_srt_MinimumMember_0d4c7ffd-ab28-4323-9395-2364a0d22f43" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_a694baf1-410a-4a17-8bae-e573e8b41d11" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_850c923c-e1b4-4981-b349-0ee558d3e3a8" xlink:to="loc_srt_MaximumMember_a694baf1-410a-4a17-8bae-e573e8b41d11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_3e2f7c53-56b0-4f54-a999-a016c4b25b18" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4873e176-b716-45ac-a79f-835e237ae72c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_3e2f7c53-56b0-4f54-a999-a016c4b25b18" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1_8bb245db-e7b6-40d6-8241-77db466e3cd5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4873e176-b716-45ac-a79f-835e237ae72c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1_8bb245db-e7b6-40d6-8241-77db466e3cd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_c87d72a1-4a7b-4062-af58-ff6d25b86d7a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4873e176-b716-45ac-a79f-835e237ae72c" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_c87d72a1-4a7b-4062-af58-ff6d25b86d7a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_cf889c1e-e7e7-4612-b643-a59702dccbe5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4873e176-b716-45ac-a79f-835e237ae72c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_cf889c1e-e7e7-4612-b643-a59702dccbe5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_e7450d08-c102-4605-b2da-88f51d24d2c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4873e176-b716-45ac-a79f-835e237ae72c" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_e7450d08-c102-4605-b2da-88f51d24d2c9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_a9ef1895-a631-4444-80a2-b230731dbf16" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4873e176-b716-45ac-a79f-835e237ae72c" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_a9ef1895-a631-4444-80a2-b230731dbf16" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_c39e191b-4b9a-4830-b54f-8ceb4ec6fe86" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4873e176-b716-45ac-a79f-835e237ae72c" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_c39e191b-4b9a-4830-b54f-8ceb4ec6fe86" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_eb479c3a-64eb-4988-b5db-46a2349d7461" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4873e176-b716-45ac-a79f-835e237ae72c" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_eb479c3a-64eb-4988-b5db-46a2349d7461" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7fd6c88d-7510-42ea-8aab-da3583c24655" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4873e176-b716-45ac-a79f-835e237ae72c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7fd6c88d-7510-42ea-8aab-da3583c24655" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_4c25a034-919b-468a-a5de-c32099a16641" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4873e176-b716-45ac-a79f-835e237ae72c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_4c25a034-919b-468a-a5de-c32099a16641" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_1d49bc82-a7f4-43c9-89fa-ea68c6b2a390" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_4873e176-b716-45ac-a79f-835e237ae72c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_1d49bc82-a7f4-43c9-89fa-ea68c6b2a390" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/ShareBasedCompensationSummaryofRestrictedStockandPerformanceActivityDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#ShareBasedCompensationSummaryofRestrictedStockandPerformanceActivityDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/ShareBasedCompensationSummaryofRestrictedStockandPerformanceActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_dde4818c-dbd9-47ed-9f8a-c3a1561ec11f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_21018caf-bee5-4956-8e5c-8017b1cb2ffb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_dde4818c-dbd9-47ed-9f8a-c3a1561ec11f" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_21018caf-bee5-4956-8e5c-8017b1cb2ffb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_7f142857-fbd1-4c7f-97ed-69830a108338" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_21018caf-bee5-4956-8e5c-8017b1cb2ffb" xlink:to="loc_us-gaap_AwardTypeAxis_7f142857-fbd1-4c7f-97ed-69830a108338" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7f142857-fbd1-4c7f-97ed-69830a108338_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_7f142857-fbd1-4c7f-97ed-69830a108338" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_7f142857-fbd1-4c7f-97ed-69830a108338_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2be0b177-e653-4c66-8478-a3acae496b8e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_7f142857-fbd1-4c7f-97ed-69830a108338" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2be0b177-e653-4c66-8478-a3acae496b8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_RestrictedStockUnitsAndRestrictedStockAwardsMember_982742e3-d48c-424d-b84b-a1158b93e9fe" xlink:href="fi-20251231.xsd#fi_RestrictedStockUnitsAndRestrictedStockAwardsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2be0b177-e653-4c66-8478-a3acae496b8e" xlink:to="loc_fi_RestrictedStockUnitsAndRestrictedStockAwardsMember_982742e3-d48c-424d-b84b-a1158b93e9fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_a7f93c15-aa7d-43e1-8c2e-932ffe8f4b0e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2be0b177-e653-4c66-8478-a3acae496b8e" xlink:to="loc_us-gaap_PerformanceSharesMember_a7f93c15-aa7d-43e1-8c2e-932ffe8f4b0e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_57baa854-f49f-4aeb-a71a-4522727f307a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_dde4818c-dbd9-47ed-9f8a-c3a1561ec11f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_57baa854-f49f-4aeb-a71a-4522727f307a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_08715c59-a470-4427-87bf-6a7ff02d3c6d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_57baa854-f49f-4aeb-a71a-4522727f307a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_08715c59-a470-4427-87bf-6a7ff02d3c6d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_1d0d2d77-1dfa-4179-91e5-740824318217" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_57baa854-f49f-4aeb-a71a-4522727f307a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_1d0d2d77-1dfa-4179-91e5-740824318217" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_1660c744-f799-4068-8fe2-0bccdec4627f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_57baa854-f49f-4aeb-a71a-4522727f307a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_1660c744-f799-4068-8fe2-0bccdec4627f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_1d6af547-a1dc-4dd7-a6be-7016765984be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_57baa854-f49f-4aeb-a71a-4522727f307a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_1d6af547-a1dc-4dd7-a6be-7016765984be" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_882f3ba1-b745-423b-a762-167bde731191" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_fdd8db76-c169-491a-a1b2-a36aac4fe62c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_dde4818c-dbd9-47ed-9f8a-c3a1561ec11f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_fdd8db76-c169-491a-a1b2-a36aac4fe62c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_abc40313-4fb5-45af-9404-49a7fbaa3bb7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_fdd8db76-c169-491a-a1b2-a36aac4fe62c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_abc40313-4fb5-45af-9404-49a7fbaa3bb7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_e1f9c53f-38cc-4660-88af-c235b30dfa60" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_fdd8db76-c169-491a-a1b2-a36aac4fe62c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_e1f9c53f-38cc-4660-88af-c235b30dfa60" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_c0269689-ba44-40d1-8209-6fd4b0fb5681" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_fdd8db76-c169-491a-a1b2-a36aac4fe62c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_c0269689-ba44-40d1-8209-6fd4b0fb5681" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_949ac536-765c-40ec-83e4-1fe71f673f35" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_fdd8db76-c169-491a-a1b2-a36aac4fe62c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_949ac536-765c-40ec-83e4-1fe71f673f35" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_3dd7b591-f9a4-422a-98ac-17d522f68b3f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/IncomeTaxesOperatingLossCarryforwardsGeneralBusinessCreditCarryforwardsandTaxCreditCarryforwardsDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#IncomeTaxesOperatingLossCarryforwardsGeneralBusinessCreditCarryforwardsandTaxCreditCarryforwardsDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/IncomeTaxesOperatingLossCarryforwardsGeneralBusinessCreditCarryforwardsandTaxCreditCarryforwardsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxContingencyLineItems_9c6e0b32-8e98-481c-ad0e-da0f4863e63f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxContingencyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxContingencyTable_de5bf473-3ebb-44e4-870d-4fbe20bbeb65" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxContingencyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_9c6e0b32-8e98-481c-ad0e-da0f4863e63f" xlink:to="loc_us-gaap_IncomeTaxContingencyTable_de5bf473-3ebb-44e4-870d-4fbe20bbeb65" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodAxis_63564fdd-270c-4eca-896c-52b110ee61a9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxPeriodAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxContingencyTable_de5bf473-3ebb-44e4-870d-4fbe20bbeb65" xlink:to="loc_us-gaap_TaxPeriodAxis_63564fdd-270c-4eca-896c-52b110ee61a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodDomain_63564fdd-270c-4eca-896c-52b110ee61a9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TaxPeriodAxis_63564fdd-270c-4eca-896c-52b110ee61a9" xlink:to="loc_us-gaap_TaxPeriodDomain_63564fdd-270c-4eca-896c-52b110ee61a9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxPeriodDomain_e0b9de7a-a848-45a6-820d-5b0d04395d83" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxPeriodDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TaxPeriodAxis_63564fdd-270c-4eca-896c-52b110ee61a9" xlink:to="loc_us-gaap_TaxPeriodDomain_e0b9de7a-a848-45a6-820d-5b0d04395d83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_TaxYear2026Through2045Member_6ab03afa-98ec-4643-8637-79f8b5e1a7dc" xlink:href="fi-20251231.xsd#fi_TaxYear2026Through2045Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxPeriodDomain_e0b9de7a-a848-45a6-820d-5b0d04395d83" xlink:to="loc_fi_TaxYear2026Through2045Member_6ab03afa-98ec-4643-8637-79f8b5e1a7dc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_010a82f9-bf71-4705-bf70-386703fece3b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxContingencyTable_de5bf473-3ebb-44e4-870d-4fbe20bbeb65" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_010a82f9-bf71-4705-bf70-386703fece3b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_010a82f9-bf71-4705-bf70-386703fece3b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_010a82f9-bf71-4705-bf70-386703fece3b" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_010a82f9-bf71-4705-bf70-386703fece3b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_86447492-1595-41b8-9733-f9c7f1035baa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_010a82f9-bf71-4705-bf70-386703fece3b" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_86447492-1595-41b8-9733-f9c7f1035baa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DomesticCountryMember_2409348d-b7a1-4dcd-846d-6f2b9ca46ae9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DomesticCountryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_86447492-1595-41b8-9733-f9c7f1035baa" xlink:to="loc_us-gaap_DomesticCountryMember_2409348d-b7a1-4dcd-846d-6f2b9ca46ae9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_c61bce36-692c-42cd-9873-a8b59985a076" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DomesticCountryMember_2409348d-b7a1-4dcd-846d-6f2b9ca46ae9" xlink:to="loc_country_US_c61bce36-692c-42cd-9873-a8b59985a076" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StateAndLocalJurisdictionMember_2bad0838-aa10-4cb3-a3b2-227629f6e7a9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StateAndLocalJurisdictionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DomesticCountryMember_2409348d-b7a1-4dcd-846d-6f2b9ca46ae9" xlink:to="loc_us-gaap_StateAndLocalJurisdictionMember_2bad0838-aa10-4cb3-a3b2-227629f6e7a9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCountryMember_fc4e3fc3-ed76-470d-97ed-34daec0bba62" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignCountryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_86447492-1595-41b8-9733-f9c7f1035baa" xlink:to="loc_us-gaap_ForeignCountryMember_fc4e3fc3-ed76-470d-97ed-34daec0bba62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignTaxJurisdictionOtherMember_019c436c-9402-77e7-a06a-59b676ca75f8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ForeignTaxJurisdictionOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ForeignCountryMember_fc4e3fc3-ed76-470d-97ed-34daec0bba62" xlink:to="loc_us-gaap_ForeignTaxJurisdictionOtherMember_019c436c-9402-77e7-a06a-59b676ca75f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsComponentsAbstract_6d4a5e41-b0c0-4968-b1b6-eb91f3819b32" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsComponentsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_9c6e0b32-8e98-481c-ad0e-da0f4863e63f" xlink:to="loc_us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsComponentsAbstract_6d4a5e41-b0c0-4968-b1b6-eb91f3819b32" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwards_e3db46f2-adc8-4786-947b-46eee7c647c9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingLossCarryforwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsComponentsAbstract_6d4a5e41-b0c0-4968-b1b6-eb91f3819b32" xlink:to="loc_us-gaap_OperatingLossCarryforwards_e3db46f2-adc8-4786-947b-46eee7c647c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxCreditCarryforwardAmount_cfa58c22-25f4-40e9-af52-7077bc21334c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TaxCreditCarryforwardAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_9c6e0b32-8e98-481c-ad0e-da0f4863e63f" xlink:to="loc_us-gaap_TaxCreditCarryforwardAmount_cfa58c22-25f4-40e9-af52-7077bc21334c" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/CommitmentsandContingenciesDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#CommitmentsandContingenciesDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/CommitmentsandContingenciesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_6d6efb9c-2130-41f0-9251-15d38533abb9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_e0468d68-8a53-46c8-baa4-2a37e963ecfe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_6d6efb9c-2130-41f0-9251-15d38533abb9" xlink:to="loc_us-gaap_LossContingenciesTable_e0468d68-8a53-46c8-baa4-2a37e963ecfe" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseAxis_8acf2256-36d8-4702-9a5d-c60a82617020" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_e0468d68-8a53-46c8-baa4-2a37e963ecfe" xlink:to="loc_srt_LitigationCaseAxis_8acf2256-36d8-4702-9a5d-c60a82617020" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_8acf2256-36d8-4702-9a5d-c60a82617020_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_LitigationCaseAxis_8acf2256-36d8-4702-9a5d-c60a82617020" xlink:to="loc_srt_LitigationCaseTypeDomain_8acf2256-36d8-4702-9a5d-c60a82617020_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_LitigationCaseTypeDomain_4959ddb4-6c83-4c73-85cc-b089a8b8884f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_LitigationCaseTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_LitigationCaseAxis_8acf2256-36d8-4702-9a5d-c60a82617020" xlink:to="loc_srt_LitigationCaseTypeDomain_4959ddb4-6c83-4c73-85cc-b089a8b8884f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_SubsidiaryMerchantMattersMember_e083b4fb-4948-46e9-a201-7507a62c4924" xlink:href="fi-20251231.xsd#fi_SubsidiaryMerchantMattersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_LitigationCaseTypeDomain_4959ddb4-6c83-4c73-85cc-b089a8b8884f" xlink:to="loc_fi_SubsidiaryMerchantMattersMember_e083b4fb-4948-46e9-a201-7507a62c4924" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_364ec622-3784-4500-811c-bd4d020737fa" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_e0468d68-8a53-46c8-baa4-2a37e963ecfe" xlink:to="loc_srt_RangeAxis_364ec622-3784-4500-811c-bd4d020737fa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_364ec622-3784-4500-811c-bd4d020737fa_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_364ec622-3784-4500-811c-bd4d020737fa" xlink:to="loc_srt_RangeMember_364ec622-3784-4500-811c-bd4d020737fa_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_a6d54ed4-2013-4b2a-8531-5142ea6b8475" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_364ec622-3784-4500-811c-bd4d020737fa" xlink:to="loc_srt_RangeMember_a6d54ed4-2013-4b2a-8531-5142ea6b8475" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_fc9919a9-7c73-4c21-abda-06bc864a436c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_a6d54ed4-2013-4b2a-8531-5142ea6b8475" xlink:to="loc_srt_MinimumMember_fc9919a9-7c73-4c21-abda-06bc864a436c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_34e08b91-3653-46a3-b0f7-9c85c87faa81" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_a6d54ed4-2013-4b2a-8531-5142ea6b8475" xlink:to="loc_srt_MaximumMember_34e08b91-3653-46a3-b0f7-9c85c87faa81" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_0df0c7d7-fc5a-463f-bf60-08eede84aced" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_6d6efb9c-2130-41f0-9251-15d38533abb9" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_0df0c7d7-fc5a-463f-bf60-08eede84aced" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyEstimateOfPossibleLoss_cb854ead-fd67-4ffa-b150-9c04eea5bc14" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LossContingencyEstimateOfPossibleLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_6d6efb9c-2130-41f0-9251-15d38533abb9" xlink:to="loc_us-gaap_LossContingencyEstimateOfPossibleLoss_cb854ead-fd67-4ffa-b150-9c04eea5bc14" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability_6a688e90-09e5-40a7-a2ef-a872797cde8f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_6d6efb9c-2130-41f0-9251-15d38533abb9" xlink:to="loc_us-gaap_FairValueDisclosureOffbalanceSheetRisksAmountLiability_6a688e90-09e5-40a7-a2ef-a872797cde8f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/RelatedPartyTransactionsDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#RelatedPartyTransactionsDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/RelatedPartyTransactionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_fa767caf-3861-4bd4-bd71-41162b4e36cd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3be9c342-3601-4eae-8a6c-772ff7bfc25c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_fa767caf-3861-4bd4-bd71-41162b4e36cd" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3be9c342-3601-4eae-8a6c-772ff7bfc25c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1bceb9e0-8c10-428b-9f88-ee6cb21bd48a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3be9c342-3601-4eae-8a6c-772ff7bfc25c" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1bceb9e0-8c10-428b-9f88-ee6cb21bd48a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_1bceb9e0-8c10-428b-9f88-ee6cb21bd48a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1bceb9e0-8c10-428b-9f88-ee6cb21bd48a" xlink:to="loc_us-gaap_RelatedPartyDomain_1bceb9e0-8c10-428b-9f88-ee6cb21bd48a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_946a00ab-591c-445a-a158-8c6e1ee1deec" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1bceb9e0-8c10-428b-9f88-ee6cb21bd48a" xlink:to="loc_us-gaap_RelatedPartyDomain_946a00ab-591c-445a-a158-8c6e1ee1deec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AffiliatedEntityMember_20077150-8612-4b76-87f7-5cd6c780bd86" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_AffiliatedEntityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_946a00ab-591c-445a-a158-8c6e1ee1deec" xlink:to="loc_srt_AffiliatedEntityMember_20077150-8612-4b76-87f7-5cd6c780bd86" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_DirectorMember_07c9aefa-dceb-4b19-99d4-e8ba2f230a4e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_DirectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_946a00ab-591c-445a-a158-8c6e1ee1deec" xlink:to="loc_srt_DirectorMember_07c9aefa-dceb-4b19-99d4-e8ba2f230a4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_ad8498f9-c43a-4136-8260-43fb75df5750" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3be9c342-3601-4eae-8a6c-772ff7bfc25c" xlink:to="loc_srt_CounterpartyNameAxis_ad8498f9-c43a-4136-8260-43fb75df5750" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_ad8498f9-c43a-4136-8260-43fb75df5750_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_ad8498f9-c43a-4136-8260-43fb75df5750" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_ad8498f9-c43a-4136-8260-43fb75df5750_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d4f6c9f9-5b82-40cb-847c-5d37394ac06e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_ad8498f9-c43a-4136-8260-43fb75df5750" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d4f6c9f9-5b82-40cb-847c-5d37394ac06e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_ValueActCapitalMasterFundLPMember_3b674a30-c0c7-4254-a964-c8f396169619" xlink:href="fi-20251231.xsd#fi_ValueActCapitalMasterFundLPMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_d4f6c9f9-5b82-40cb-847c-5d37394ac06e" xlink:to="loc_fi_ValueActCapitalMasterFundLPMember_3b674a30-c0c7-4254-a964-c8f396169619" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_549ab8b9-8ea6-43aa-b115-18e886705cb7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_fa767caf-3861-4bd4-bd71-41162b4e36cd" xlink:to="loc_us-gaap_Revenues_549ab8b9-8ea6-43aa-b115-18e886705cb7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_8bfea3a9-c411-423f-b2ea-5cd7924e2ccf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_fa767caf-3861-4bd4-bd71-41162b4e36cd" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_8bfea3a9-c411-423f-b2ea-5cd7924e2ccf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_45914127-fcab-467b-b994-807c64aa2b0d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_fa767caf-3861-4bd4-bd71-41162b4e36cd" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_45914127-fcab-467b-b994-807c64aa2b0d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_53402a9b-58a2-49f8-8e64-4c3fb12b452a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_fa767caf-3861-4bd4-bd71-41162b4e36cd" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_53402a9b-58a2-49f8-8e64-4c3fb12b452a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonValue_49e83e09-af8b-4b0e-9d8d-002c72be9caf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TreasuryStockCommonValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_fa767caf-3861-4bd4-bd71-41162b4e36cd" xlink:to="loc_us-gaap_TreasuryStockCommonValue_49e83e09-af8b-4b0e-9d8d-002c72be9caf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_6cce34da-5660-49eb-912f-465a19a0362c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_fa767caf-3861-4bd4-bd71-41162b4e36cd" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_6cce34da-5660-49eb-912f-465a19a0362c" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/BusinessSegmentInformationNarrativeDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#BusinessSegmentInformationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/BusinessSegmentInformationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_17bc35c4-303b-4e31-b97a-07719ba0040c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_142dbe7a-cff1-495a-9053-4f2b78cee52b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_17bc35c4-303b-4e31-b97a-07719ba0040c" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_142dbe7a-cff1-495a-9053-4f2b78cee52b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_cf984c77-c265-4b90-936a-29e69cf982fe" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_142dbe7a-cff1-495a-9053-4f2b78cee52b" xlink:to="loc_srt_StatementGeographicalAxis_cf984c77-c265-4b90-936a-29e69cf982fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_cf984c77-c265-4b90-936a-29e69cf982fe_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_cf984c77-c265-4b90-936a-29e69cf982fe" xlink:to="loc_srt_SegmentGeographicalDomain_cf984c77-c265-4b90-936a-29e69cf982fe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_d9e056f2-ef48-4c12-8e77-d8fdbe678cdd" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_cf984c77-c265-4b90-936a-29e69cf982fe" xlink:to="loc_srt_SegmentGeographicalDomain_d9e056f2-ef48-4c12-8e77-d8fdbe678cdd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_083de51f-1a78-4111-97da-711572bad49b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_d9e056f2-ef48-4c12-8e77-d8fdbe678cdd" xlink:to="loc_us-gaap_NonUsMember_083de51f-1a78-4111-97da-711572bad49b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_bb16affd-1d18-4f11-9f65-4b6645e635fc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_142dbe7a-cff1-495a-9053-4f2b78cee52b" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_bb16affd-1d18-4f11-9f65-4b6645e635fc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_bb16affd-1d18-4f11-9f65-4b6645e635fc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_bb16affd-1d18-4f11-9f65-4b6645e635fc" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_bb16affd-1d18-4f11-9f65-4b6645e635fc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_f824f95e-e528-462f-98d3-5f011dea1cc8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_bb16affd-1d18-4f11-9f65-4b6645e635fc" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_f824f95e-e528-462f-98d3-5f011dea1cc8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_LongLivedAssetsMember_295fbb67-514b-49e9-ac4f-59ab851f1a4c" xlink:href="fi-20251231.xsd#fi_LongLivedAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_f824f95e-e528-462f-98d3-5f011dea1cc8" xlink:to="loc_fi_LongLivedAssetsMember_295fbb67-514b-49e9-ac4f-59ab851f1a4c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_d1fd78f6-a593-409b-bcf7-d82952d0f011" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_142dbe7a-cff1-495a-9053-4f2b78cee52b" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_d1fd78f6-a593-409b-bcf7-d82952d0f011" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_d1fd78f6-a593-409b-bcf7-d82952d0f011_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_d1fd78f6-a593-409b-bcf7-d82952d0f011" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_d1fd78f6-a593-409b-bcf7-d82952d0f011_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_70f28ef4-1959-43d5-863d-127294ae7ba4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_d1fd78f6-a593-409b-bcf7-d82952d0f011" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_70f28ef4-1959-43d5-863d-127294ae7ba4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeographicConcentrationRiskMember_925dffc6-5fa0-413d-9827-32a76b830465" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeographicConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_70f28ef4-1959-43d5-863d-127294ae7ba4" xlink:to="loc_us-gaap_GeographicConcentrationRiskMember_925dffc6-5fa0-413d-9827-32a76b830465" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments_77eecf7e-ba56-484f-a70a-9440c056950c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NumberOfReportableSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_17bc35c4-303b-4e31-b97a-07719ba0040c" xlink:to="loc_us-gaap_NumberOfReportableSegments_77eecf7e-ba56-484f-a70a-9440c056950c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_2f23f401-b1c5-4aff-922e-d66faf58a42b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_17bc35c4-303b-4e31-b97a-07719ba0040c" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_2f23f401-b1c5-4aff-922e-d66faf58a42b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/BusinessSegmentInformationScheduleofSegmentReportingInformationDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#BusinessSegmentInformationScheduleofSegmentReportingInformationDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/BusinessSegmentInformationScheduleofSegmentReportingInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_14e3d572-2d1e-4f7c-82fd-218254d1268e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_25b14bb2-38d5-4ab1-930f-f20ad52fb1dc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_14e3d572-2d1e-4f7c-82fd-218254d1268e" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_25b14bb2-38d5-4ab1-930f-f20ad52fb1dc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_3d6c5272-22b7-468c-97c6-74a350bdac0f" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_25b14bb2-38d5-4ab1-930f-f20ad52fb1dc" xlink:to="loc_srt_ConsolidationItemsAxis_3d6c5272-22b7-468c-97c6-74a350bdac0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_3d6c5272-22b7-468c-97c6-74a350bdac0f_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_3d6c5272-22b7-468c-97c6-74a350bdac0f" xlink:to="loc_srt_ConsolidationItemsDomain_3d6c5272-22b7-468c-97c6-74a350bdac0f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_c313d9b8-7f6c-4efe-bb09-25604ccab539" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_3d6c5272-22b7-468c-97c6-74a350bdac0f" xlink:to="loc_srt_ConsolidationItemsDomain_c313d9b8-7f6c-4efe-bb09-25604ccab539" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_b2eb1b86-c4e1-492a-8830-938bbf07193c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_c313d9b8-7f6c-4efe-bb09-25604ccab539" xlink:to="loc_us-gaap_OperatingSegmentsMember_b2eb1b86-c4e1-492a-8830-938bbf07193c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_e2cca3c0-b8e4-4079-a299-e1d8309beac8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_c313d9b8-7f6c-4efe-bb09-25604ccab539" xlink:to="loc_us-gaap_CorporateNonSegmentMember_e2cca3c0-b8e4-4079-a299-e1d8309beac8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_b6ae15c6-842b-48f6-9cdf-9961f05238ab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_25b14bb2-38d5-4ab1-930f-f20ad52fb1dc" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_b6ae15c6-842b-48f6-9cdf-9961f05238ab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_b6ae15c6-842b-48f6-9cdf-9961f05238ab_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_b6ae15c6-842b-48f6-9cdf-9961f05238ab" xlink:to="loc_us-gaap_SegmentDomain_b6ae15c6-842b-48f6-9cdf-9961f05238ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_2a44892f-df45-4a44-8d09-236c49dd2491" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_b6ae15c6-842b-48f6-9cdf-9961f05238ab" xlink:to="loc_us-gaap_SegmentDomain_2a44892f-df45-4a44-8d09-236c49dd2491" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_MerchantSolutionsSegmentMember_02a8cd81-1a1c-4eb5-a598-cf7f9a681560" xlink:href="fi-20251231.xsd#fi_MerchantSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_2a44892f-df45-4a44-8d09-236c49dd2491" xlink:to="loc_fi_MerchantSolutionsSegmentMember_02a8cd81-1a1c-4eb5-a598-cf7f9a681560" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_FinancialSolutionsSegmentMember_d6e5586f-0b57-4b8b-8da5-1c57c5399611" xlink:href="fi-20251231.xsd#fi_FinancialSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_2a44892f-df45-4a44-8d09-236c49dd2491" xlink:to="loc_fi_FinancialSolutionsSegmentMember_d6e5586f-0b57-4b8b-8da5-1c57c5399611" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_15e3be8f-a086-4c78-8b41-e89bd9a2ed6e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_25b14bb2-38d5-4ab1-930f-f20ad52fb1dc" xlink:to="loc_srt_ProductOrServiceAxis_15e3be8f-a086-4c78-8b41-e89bd9a2ed6e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_15e3be8f-a086-4c78-8b41-e89bd9a2ed6e_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_15e3be8f-a086-4c78-8b41-e89bd9a2ed6e" xlink:to="loc_srt_ProductsAndServicesDomain_15e3be8f-a086-4c78-8b41-e89bd9a2ed6e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_9db01fa8-f745-46ad-a3f1-bce0676239e0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_15e3be8f-a086-4c78-8b41-e89bd9a2ed6e" xlink:to="loc_srt_ProductsAndServicesDomain_9db01fa8-f745-46ad-a3f1-bce0676239e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_ProcessingAndServicesMember_626a26fa-a425-4b77-ab70-adacb96e8a08" xlink:href="fi-20251231.xsd#fi_ProcessingAndServicesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_9db01fa8-f745-46ad-a3f1-bce0676239e0" xlink:to="loc_fi_ProcessingAndServicesMember_626a26fa-a425-4b77-ab70-adacb96e8a08" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductMember_7043b401-914a-44b0-96fc-0ddf455e56a8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProductMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_9db01fa8-f745-46ad-a3f1-bce0676239e0" xlink:to="loc_us-gaap_ProductMember_7043b401-914a-44b0-96fc-0ddf455e56a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_82a1d9aa-138e-45ad-9163-4f041c5e06ef" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_14e3d572-2d1e-4f7c-82fd-218254d1268e" xlink:to="loc_us-gaap_RevenuesAbstract_82a1d9aa-138e-45ad-9163-4f041c5e06ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_666649bb-7fbe-41af-b6ea-754998d3cba6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_82a1d9aa-138e-45ad-9163-4f041c5e06ef" xlink:to="loc_us-gaap_Revenues_666649bb-7fbe-41af-b6ea-754998d3cba6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_5ce14741-48bf-4f5b-805d-62b1a5afe5a6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_14e3d572-2d1e-4f7c-82fd-218254d1268e" xlink:to="loc_us-gaap_OperatingExpensesAbstract_5ce14741-48bf-4f5b-805d-62b1a5afe5a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_1d2b733d-c24f-4b63-a1ee-af91e0f3ba65" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_5ce14741-48bf-4f5b-805d-62b1a5afe5a6" xlink:to="loc_us-gaap_LaborAndRelatedExpense_1d2b733d-c24f-4b63-a1ee-af91e0f3ba65" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DirectOperatingCosts_18ac22a3-ef37-4703-8a7b-13ce65fd6ce9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DirectOperatingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_5ce14741-48bf-4f5b-805d-62b1a5afe5a6" xlink:to="loc_us-gaap_DirectOperatingCosts_18ac22a3-ef37-4703-8a7b-13ce65fd6ce9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_da27a00a-676a-4028-bcd8-c88f0b4b96b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_5ce14741-48bf-4f5b-805d-62b1a5afe5a6" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_da27a00a-676a-4028-bcd8-c88f0b4b96b6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCostAndExpenseOperating_371c0758-cc21-4367-8c78-e5c87dcca112" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherCostAndExpenseOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_5ce14741-48bf-4f5b-805d-62b1a5afe5a6" xlink:to="loc_us-gaap_OtherCostAndExpenseOperating_371c0758-cc21-4367-8c78-e5c87dcca112" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_99c22a39-b477-48c8-a5ef-eb0977ace5a9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_14e3d572-2d1e-4f7c-82fd-218254d1268e" xlink:to="loc_us-gaap_OperatingIncomeLoss_99c22a39-b477-48c8-a5ef-eb0977ace5a9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_0abc2c9c-a399-4306-aef7-2ddf778c8c31" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestIncomeExpenseNonoperatingNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_14e3d572-2d1e-4f7c-82fd-218254d1268e" xlink:to="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_0abc2c9c-a399-4306-aef7-2ddf778c8c31" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_11afbe44-7061-4e82-b9f0-b4f57f6d148b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_14e3d572-2d1e-4f7c-82fd-218254d1268e" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_11afbe44-7061-4e82-b9f0-b4f57f6d148b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_584dafd1-34d3-4ffb-915f-2afce6cc0cdc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_14e3d572-2d1e-4f7c-82fd-218254d1268e" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_584dafd1-34d3-4ffb-915f-2afce6cc0cdc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_fi_DepreciationDepletionAndAmortizationAdjusted_c1b80a77-0304-4ea2-b998-46c49a61d6e1" xlink:href="fi-20251231.xsd#fi_DepreciationDepletionAndAmortizationAdjusted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_14e3d572-2d1e-4f7c-82fd-218254d1268e" xlink:to="loc_fi_DepreciationDepletionAndAmortizationAdjusted_c1b80a77-0304-4ea2-b998-46c49a61d6e1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentExpenditureAdditionToLongLivedAssets_a052e155-849f-491d-ada7-66fe3176888e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SegmentExpenditureAdditionToLongLivedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_14e3d572-2d1e-4f7c-82fd-218254d1268e" xlink:to="loc_us-gaap_SegmentExpenditureAdditionToLongLivedAssets_a052e155-849f-491d-ada7-66fe3176888e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestChangeInRedemptionValue_77ae7f21-9228-4dc5-9af9-30430323f60b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MinorityInterestChangeInRedemptionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_14e3d572-2d1e-4f7c-82fd-218254d1268e" xlink:to="loc_us-gaap_MinorityInterestChangeInRedemptionValue_77ae7f21-9228-4dc5-9af9-30430323f60b" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.fiserv.com/role/ScheduleIIValuationandQualifyingAccountsDetails" xlink:type="simple" xlink:href="fi-20251231.xsd#ScheduleIIValuationandQualifyingAccountsDetails"/>
  <link:definitionLink xlink:role="http://www.fiserv.com/role/ScheduleIIValuationandQualifyingAccountsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_ae82e0f2-8538-40f2-a9aa-699d9b9ee62c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ValuationAndQualifyingAccountsDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_e988cd35-8e51-4229-a483-f3fb1d00f4f4" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ValuationAndQualifyingAccountsDisclosureTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_ae82e0f2-8538-40f2-a9aa-699d9b9ee62c" xlink:to="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_e988cd35-8e51-4229-a483-f3fb1d00f4f4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_19212142-d048-49be-981d-92ce2f89ad3f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_e988cd35-8e51-4229-a483-f3fb1d00f4f4" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_19212142-d048-49be-981d-92ce2f89ad3f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_19212142-d048-49be-981d-92ce2f89ad3f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_19212142-d048-49be-981d-92ce2f89ad3f" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_19212142-d048-49be-981d-92ce2f89ad3f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_b7b07765-a7b5-4005-8c33-da2eeb0d7034" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_19212142-d048-49be-981d-92ce2f89ad3f" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_b7b07765-a7b5-4005-8c33-da2eeb0d7034" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember_f9cfd240-4e7a-406a-a6ed-b22c8592c22e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesDomain_b7b07765-a7b5-4005-8c33-da2eeb0d7034" xlink:to="loc_us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember_f9cfd240-4e7a-406a-a6ed-b22c8592c22e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_019c48ea-bb56-78fe-b326-cc95b7c690f1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_MovementInValuationAllowancesAndReservesRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_ae82e0f2-8538-40f2-a9aa-699d9b9ee62c" xlink:to="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_019c48ea-bb56-78fe-b326-cc95b7c690f1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesBalance_542ae40a-fcae-4a7d-896d-72b30888d7ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesBalance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_019c48ea-bb56-78fe-b326-cc95b7c690f1" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesBalance_542ae40a-fcae-4a7d-896d-72b30888d7ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense_8c6e8719-24e9-4e02-867e-e2dd3f570a00" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_019c48ea-bb56-78fe-b326-cc95b7c690f1" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense_8c6e8719-24e9-4e02-867e-e2dd3f570a00" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesChargedToOtherAccounts_985a11bc-9d49-4752-81e0-f001b974b5cc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesChargedToOtherAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_019c48ea-bb56-78fe-b326-cc95b7c690f1" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesChargedToOtherAccounts_985a11bc-9d49-4752-81e0-f001b974b5cc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDeductions_ca3fa334-73f3-4898-b91d-b4a792926956" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesDeductions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_019c48ea-bb56-78fe-b326-cc95b7c690f1" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDeductions_ca3fa334-73f3-4898-b91d-b4a792926956" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesBalance_831ecc85-5b51-48ef-a146-1366b81e6693" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ValuationAllowancesAndReservesBalance"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-roles-2025.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:type="arc" order="691"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract" xlink:to="loc_us-gaap_OtherAssetsNoncurrent" xlink:type="arc" order="101"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet" xlink:type="arc" order="102"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:to="loc_us-gaap_LongTermDebtAndCapitalLeaseObligationsCurrent" xlink:type="arc" order="41"/>
  </link:definitionLink>
</link:linkbase>
