<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-05-16</periodOfReport>
    <issuer>
        <issuerCik>0000732713</issuerCik>
        <issuerName>BELLSOUTH CORP</issuerName>
        <issuerTradingSymbol>BLS</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId>
            <rptOwnerCik>0001162744</rptOwnerCik>
            <rptOwnerName>FELDSTEIN KATHLEEN F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther></reportingOwnerRelationship></reportingOwner><derivativeSecurity><securityTitle><value>Phantom Deferral Shares</value></securityTitle><conversionOrExercisePrice><value>0</value><footnoteId id="F3"/></conversionOrExercisePrice><transactionDate><value>2003-05-16</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved><footnoteId id="F1"/></transactionCoding><transactionAmounts><transactionShares><value>67.8068</value></transactionShares><transactionValue><value>26.546</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2010-01-01</value></exerciseDate><expirationDate><value>2010-01-01</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>67.8068</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>13061.4622</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><footnotes><footnote id="F1">SHARES OF PHANTOM STOCK ACQUIRED PURSUANT TO BELLSOUTH CORPORATION DEFERRAL PLAN IN TRANSACTION EXEMPT UNDER RULE 16b-3(d).</footnote><footnote id="F2">INCLUDES SHARES OF PHANTOM STOCK ACQUIRED AS A RESULT OF REINVESTMENT OF DIVIDENDS ACCRUED ON PHANTOM SHARES PREVIOUSLY ACQUIRED UNDER VARIOUS DEFERRAL PLANS IN TRANSACTIONS EXEMPT UNDER RULE 16b-3 AND DEFERRED INTO PHANTOM ACCOUNT.</footnote><footnote id="F3">SHARES OF PHANTOM STOCK CONVERT TO COMMON STOCK ON A ONE-FOR-ONE BASIS.</footnote></footnotes><ownerSignature><signatureName>Marcy A. Bass, Attorney in Fact</signatureName><signatureDate>2003-05-20</signatureDate></ownerSignature></ownershipDocument>

