<SUBMISSION>
<ACCESSION-NUMBER>0001179110-08-013422
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20080703
<FILING-DATE>20080707
<DATE-OF-FILING-DATE-CHANGE>20080707
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>LIBERTY MEDIA CORP
<CIK>0001355096
<ASSIGNED-SIC>4841
<IRS-NUMBER>841288730
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>12300 LIBERTY BOULEVARD
<CITY>ENGLEWOOD
<STATE>CO
<ZIP>80112
<PHONE>7208755400
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>12300 LIBERTY BOULEVARD
<CITY>ENGLEWOOD
<STATE>CO
<ZIP>80112
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>Liberty Media Holding CORP
<DATE-CHANGED>20060303
</FORMER-COMPANY>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>MALONE JOHN C
<CIK>0000937797
<STATE-OF-INCORPORATION>CO
<FISCAL-YEAR-END>1231
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-33982
<FILM-NUMBER>08940923
</FILING-VALUES>
<BUSINESS-ADDRESS>
<PHONE>7208755400
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>LIBERTY MEDIA CORP
<STREET2>12300 LIBERTY BLVD
<CITY>ENGLEWOOD
<STATE>CO
<ZIP>80112
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-07-03</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001355096</issuerCik>
        <issuerName>LIBERTY MEDIA CORP</issuerName>
        <issuerTradingSymbol>LCAPA</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000937797</rptOwnerCik>
            <rptOwnerName>MALONE JOHN C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>12300 LIBERTY BLVD.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ENGLEWOOD</rptOwnerCity>
            <rptOwnerState>CO</rptOwnerState>
            <rptOwnerZipCode>80112</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chairman of the Board</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Series A Liberty Capital Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-07-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3827760</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.309</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7228748</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Series A Liberty Capital Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>75252</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Spouse</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Series A Liberty Capital Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>165</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Trust</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Series A Liberty Capital Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>200</value>
                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By 401(k) Savings Plan</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Series B Liberty Capital Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-07-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>3400</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.40</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5294280</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Series B Liberty Capital Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>170471</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Spouse</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The purchases reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on June 30, 2008.</footnote>
        <footnote id="F2">The price reflects a weighted average of purchases made at prices ranging from $14.27 to $14.50.  The Reporting Person agrees to provide upon request by the staff of the Securities and Exchange Commission, the Issuer, or a security holder of the Issuer, information regarding the number of shares purchased at each separate price.</footnote>
        <footnote id="F3">The Reporting Person disclaims beneficial ownership of these shares owned by his spouse.</footnote>
        <footnote id="F4">The Reporting Person is the sole trustee of and, with his spouse, retains a unitrust interest in the trust.</footnote>
        <footnote id="F5">The number of shares represents equivalent shares based on the fair market value of the shares of Series A Liberty Capital common stock held by the unitized stock fund under the Issuer's 401(k) Savings Plan based on a report from the Plan Administrator dated as of June 30, 2008.  The Reporting Person has an interest in the unitized fund, which holds shares of Series A Liberty Capital common stock, Series A Liberty Interactive common stock, Series A Liberty Entertainment common stock and short-term investments.</footnote>
    </footnotes>

    <remarks>The trading symbols for the Issuer's Series A and Series B common stock are, respectively, LCAPA and LCAPB.</remarks>

    <ownerSignature>
        <signatureName>/s/ John C. Malone</signatureName>
        <signatureDate>2008-07-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
