<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0206</schemaVersion>

    <documentType>3/A</documentType>

    <periodOfReport>2020-01-30</periodOfReport>

    <dateOfOriginalSubmission>2020-02-06</dateOfOriginalSubmission>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000035527</issuerCik>
        <issuerName>FIFTH THIRD BANCORP</issuerName>
        <issuerTradingSymbol>FITB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001162401</rptOwnerCik>
            <rptOwnerName>HARVEY THOMAS H</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>38 FOUNTAIN SQUARE PLAZA</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>CINCINNATI</rptOwnerCity>
            <rptOwnerState>OH</rptOwnerState>
            <rptOwnerZipCode>45263</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>126242</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The purpose of this filing is to report that the Form 3 filed on February 6, 2020 at 16:17:25  (SEC Accession number 0000035527-20-000018 ) was erroneously filed due to a technical software error. The actual Form 3 for the Reporting Person was filed on March 25, 2019 at 16:25:40 (SEC Accession number 0000035527-19-000029).  As of March 6, 2020, the Reporting Person owned 126,242 shares of common stock.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Christopher R. England, as Attorney-in-Fact for Thomas H. Harvey</signatureName>
        <signatureDate>2020-03-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
