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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-02-01</periodOfReport>

    <issuer>
        <issuerCik>0000732713</issuerCik>
        <issuerName>BELLSOUTH CORP</issuerName>
        <issuerTradingSymbol>BLS</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001026931</rptOwnerCik>
            <rptOwnerName>BLANCHARD JAMES H</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1111 BAY AVENUE, SUITE 500</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>COLUMBUS</rptOwnerCity>
            <rptOwnerState>GA</rptOwnerState>
            <rptOwnerZipCode>31901</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Deferral Shares</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-02-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>764.1212</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>28.575</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2010-01-01</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2019-01-01</value>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>764.1212</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>41696.2612</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">SHARES OF PHANTOM STOCK CONVERT TO COMMON STOCK ON A ONE-FOR-ONE BASIS.</footnote>
        <footnote id="F2">SHARES OF PHANTOM STOCK ACQUIRED PURSUANT TO BELLSOUTH CORPORATION DEFERRAL PLAN IN TRANSACTIONS EXEMPT UNDER RULE 16b-3(d).</footnote>
        <footnote id="F3">PAID OUT 1/10TH PER YEAR BEGINNING ON 1/1/2010.</footnote>
        <footnote id="F4">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>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Marcy A. Bass, Attorney in Fact</signatureName>
        <signatureDate>2006-02-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2006-02-01
0000732713
BELLSOUTH CORP
BLS
0001026931
BLANCHARD JAMES H
1111 BAY AVENUE, SUITE 500
COLUMBUS
GA
31901
1
0
0
0
Phantom Deferral Shares
2006-02-01
4
A
0
764.1212
28.575
A
2010-01-01
2019-01-01
Common Stock
764.1212
41696.2612
D
SHARES OF PHANTOM STOCK CONVERT TO COMMON STOCK ON A ONE-FOR-ONE BASIS.
SHARES OF PHANTOM STOCK ACQUIRED PURSUANT TO BELLSOUTH CORPORATION DEFERRAL PLAN IN TRANSACTIONS EXEMPT UNDER RULE 16b-3(d).
PAID OUT 1/10TH PER YEAR BEGINNING ON 1/1/2010.
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.
Marcy A. Bass, Attorney in Fact
2006-02-02