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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019f80de-7a6a-7645-8784-5a5bbd7eb434,g:9bdd3453-374d-4a43-b370-3351d21b61b5-->
<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.firsthorizon.com/role/Cover" xlink:type="simple" xlink:href="fhn-20261015.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.firsthorizon.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_019f80de-7a6a-74b8-be66-5403331cc330" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_DocumentInformationTable_019f80de-7a6a-74b8-be66-5403331cc330" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019f80de-7a6a-721c-a8c7-ed9f38616f92" 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_019f80de-7a6a-74b8-be66-5403331cc330" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019f80de-7a6a-721c-a8c7-ed9f38616f92" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019f80de-7a6a-721c-a8c7-ed9f38616f92_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_019f80de-7a6a-721c-a8c7-ed9f38616f92" xlink:to="loc_us-gaap_ClassOfStockDomain_019f80de-7a6a-721c-a8c7-ed9f38616f92_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019f80de-7a6a-7ea0-ae7d-8c2631cf14bd" 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_019f80de-7a6a-721c-a8c7-ed9f38616f92" xlink:to="loc_us-gaap_ClassOfStockDomain_019f80de-7a6a-7ea0-ae7d-8c2631cf14bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fhn_A625ParValueCommonCapitalStockMember_019f80de-7a6a-7dac-86d1-6c6f9d56c209" xlink:href="fhn-20261015.xsd#fhn_A625ParValueCommonCapitalStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019f80de-7a6a-7ea0-ae7d-8c2631cf14bd" xlink:to="loc_fhn_A625ParValueCommonCapitalStockMember_019f80de-7a6a-7dac-86d1-6c6f9d56c209" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_fhn_DepositorySharesEachRepresentingA14000thInterestInAShareOfNonCumulativePerpetualPreferredStockSeriesEMember_019f80de-7a6a-7c99-bc44-92067cd58871" xlink:href="fhn-20261015.xsd#fhn_DepositorySharesEachRepresentingA14000thInterestInAShareOfNonCumulativePerpetualPreferredStockSeriesEMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019f80de-7a6a-7ea0-ae7d-8c2631cf14bd" xlink:to="loc_fhn_DepositorySharesEachRepresentingA14000thInterestInAShareOfNonCumulativePerpetualPreferredStockSeriesEMember_019f80de-7a6a-7c99-bc44-92067cd58871" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_fhn_DepositorySharesEachRepresentingA14000thInterestInAShareOfNonCumulativePerpetualPreferredStockSeriesFMember_019f80de-7a6a-7fad-9523-079db73924a7" xlink:href="fhn-20261015.xsd#fhn_DepositorySharesEachRepresentingA14000thInterestInAShareOfNonCumulativePerpetualPreferredStockSeriesFMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019f80de-7a6a-7ea0-ae7d-8c2631cf14bd" xlink:to="loc_fhn_DepositorySharesEachRepresentingA14000thInterestInAShareOfNonCumulativePerpetualPreferredStockSeriesFMember_019f80de-7a6a-7fad-9523-079db73924a7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_fhn_DepositorySharesEachRepresentingA14000thInterestInAShareOfNonCumulativePerpetualPreferredStockSeriesHMember_019f80de-7a6a-7b42-bc27-acf713e2c0ee" xlink:href="fhn-20261015.xsd#fhn_DepositorySharesEachRepresentingA14000thInterestInAShareOfNonCumulativePerpetualPreferredStockSeriesHMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019f80de-7a6a-7ea0-ae7d-8c2631cf14bd" xlink:to="loc_fhn_DepositorySharesEachRepresentingA14000thInterestInAShareOfNonCumulativePerpetualPreferredStockSeriesHMember_019f80de-7a6a-7b42-bc27-acf713e2c0ee" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019f80de-7a6a-77b9-8286-8c87003a8cdb" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_DocumentType_019f80de-7a6a-77b9-8286-8c87003a8cdb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019f80de-7a6a-7ee1-bf98-3ea4b41e1de6" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_DocumentPeriodEndDate_019f80de-7a6a-7ee1-bf98-3ea4b41e1de6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019f80de-7a6a-7dad-b322-f26dcce24885" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_EntityRegistrantName_019f80de-7a6a-7dad-b322-f26dcce24885" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019f80de-7a6a-7037-a093-202657eda5ff" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019f80de-7a6a-7037-a093-202657eda5ff" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019f80de-7a6a-7b67-9306-8180ca6148a3" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_EntityFileNumber_019f80de-7a6a-7b67-9306-8180ca6148a3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019f80de-7a6a-7cbc-b377-64b5d0d7a21a" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_EntityTaxIdentificationNumber_019f80de-7a6a-7cbc-b377-64b5d0d7a21a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019f80de-7a6a-7567-a403-dca980014a87" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_EntityAddressAddressLine1_019f80de-7a6a-7567-a403-dca980014a87" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019f80de-7a6a-71ff-a48e-1af358f0c24e" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_EntityAddressCityOrTown_019f80de-7a6a-71ff-a48e-1af358f0c24e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019f80de-7a6a-7730-b58c-f97c337e52d8" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_EntityAddressStateOrProvince_019f80de-7a6a-7730-b58c-f97c337e52d8" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019f80de-7a6a-7a27-bb8a-860fa932c3fc" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_EntityAddressPostalZipCode_019f80de-7a6a-7a27-bb8a-860fa932c3fc" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019f80de-7a6a-72ca-9914-1c766682c5dd" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_CityAreaCode_019f80de-7a6a-72ca-9914-1c766682c5dd" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019f80de-7a6a-7914-b686-90558df9bbec" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_LocalPhoneNumber_019f80de-7a6a-7914-b686-90558df9bbec" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_WrittenCommunications_019f80de-7a6a-785f-92d0-484a1c56bc83" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_WrittenCommunications"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_WrittenCommunications_019f80de-7a6a-785f-92d0-484a1c56bc83" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SolicitingMaterial_019f80de-7a6a-7524-b3c3-68818796c12f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_SolicitingMaterial"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_SolicitingMaterial_019f80de-7a6a-7524-b3c3-68818796c12f" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementTenderOffer_019f80de-7a6a-753a-89f4-462b92a34b8f" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_PreCommencementTenderOffer_019f80de-7a6a-753a-89f4-462b92a34b8f" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_PreCommencementIssuerTenderOffer_019f80de-7a6a-77b3-bcd1-24bef8f7d224" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_PreCommencementIssuerTenderOffer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_PreCommencementIssuerTenderOffer_019f80de-7a6a-77b3-bcd1-24bef8f7d224" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019f80de-7a6a-7b4a-ae72-1a62ee61b14d" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_Security12bTitle_019f80de-7a6a-7b4a-ae72-1a62ee61b14d" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019f80de-7a6a-7fa9-93fe-ea0d93596864" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_TradingSymbol_019f80de-7a6a-7fa9-93fe-ea0d93596864" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019f80de-7a6a-789c-a41e-abfba09feef2" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_SecurityExchangeName_019f80de-7a6a-789c-a41e-abfba09feef2" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019f80de-7a6a-7c73-9662-2f24cd27b0dd" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_EntityEmergingGrowthCompany_019f80de-7a6a-7c73-9662-2f24cd27b0dd" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019f80de-7a6a-7619-a662-acf2f99a26ff" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_EntityCentralIndexKey_019f80de-7a6a-7619-a662-acf2f99a26ff" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019f80de-7a6a-74ef-a5fc-198acd485347" 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_019f80de-7a6a-73cc-82c4-f7595517911a" xlink:to="loc_dei_AmendmentFlag_019f80de-7a6a-74ef-a5fc-198acd485347" xlink:type="arc" order="21"/>
  </link:definitionLink>
</link:linkbase>
