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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2013-06-25</periodOfReport>

    <dateOfOriginalSubmission>2013-06-27</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000096223</issuerCik>
        <issuerName>LEUCADIA NATIONAL CORP</issuerName>
        <issuerTradingSymbol>LUK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000924255</rptOwnerCik>
            <rptOwnerName>STEINBERG JOSEPH S</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O LEUCADIA NATIONAL CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>520 MADISON AVENUE</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chairman of the Board</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Shares</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2292687</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2013-06-25</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>132000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>25.0058</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21109306</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See Explanation</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Reflects weighted average per share price (excluding commissions) of separately priced transactions at a range of $24.95-$25.15. Upon the request of the staff of the Commission, full information regarding the number of shares sold at each separate price will be provided.</footnote>
        <footnote id="F2">Includes 7,200 Leucadia common shares beneficially owned by a daughter of the Reporting Person, 18,762,394 Leucadia common shares held by corporations that are wholly owned by the Reporting Person, or held by corporations that are wholly owned by family trusts as to which the Reporting Person has sole voting and dispositive control, or held by such trusts, 2,339,712 Leucadia common shares held in a trust for the benefit of the Reporting Person's children as to which the Reporting Person may be deemed to be the beneficial owner and 1,200,000 Leucadia common shares which the Reporting Person has the right to acquire upon exercise of warrants.</footnote>
    </footnotes>

    <remarks>This amendment to the Form 4 filed on June 27, 2013 (the &quot;Original Form 4&quot;) is made solely to correct an error in the second line item in Item 4 of Table I (Securities Acquired (A) or Disposed (D)) from &quot;A&quot; to &quot;D&quot;. Except for the foregoing, all other information in the Original Form 4 remains the same.</remarks>

    <ownerSignature>
        <signatureName>/s/ Joseph S. Steinberg</signatureName>
        <signatureDate>2013-06-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
