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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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<SEC-DOCUMENT>0000716039-05-000117.txt : 20050812
<SEC-HEADER>0000716039-05-000117.hdr.sgml : 20050812
<ACCEPTANCE-DATETIME>20050812175859
ACCESSION NUMBER:		0000716039-05-000117
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050810
FILED AS OF DATE:		20050812
DATE AS OF CHANGE:		20050812

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			UNOCAL CORP
		CENTRAL INDEX KEY:			0000716039
		STANDARD INDUSTRIAL CLASSIFICATION:	CRUDE PETROLEUM & NATURAL GAS [1311]
		IRS NUMBER:				953825062
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0901

	BUSINESS ADDRESS:	
		STREET 1:		2141 ROSECRANS AVE
		STREET 2:		STE 4000
		CITY:			EL SEGUNDO
		STATE:			CA
		ZIP:			90245
		BUSINESS PHONE:		3107267600

	MAIL ADDRESS:	
		STREET 1:		2141 ROSECRANS AVE
		STREET 2:		STE 4000
		CITY:			EL SEGUNDO
		STATE:			CA
		ZIP:			90245

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			SUWYN MARK A
		CENTRAL INDEX KEY:			0001229684

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-08483
		FILM NUMBER:		051022979

	BUSINESS ADDRESS:	
		STREET 1:		80 SW BROADWAY
		CITY:			PORTLAND
		STATE:			OR
		ZIP:			97205
		BUSINESS PHONE:		6159865600

	MAIL ADDRESS:	
		STREET 1:		LOUISIANA-PACIFIC CORPORATION
		STREET 2:		414 UNION STREET, SUITE 1910
		CITY:			NASHVILLE
		STATE:			TN
		ZIP:			37219
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>f4forsuwy.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-08-10</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000716039</issuerCik>
        <issuerName>UNOCAL CORP</issuerName>
        <issuerTradingSymbol>UCL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001229684</rptOwnerCik>
            <rptOwnerName>SUWYN MARK A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>LOUISIANA-PACIFIC CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>805 SW BROADWAY #700</rptOwnerStreet2>
            <rptOwnerCity>PORTLAND</rptOwnerCity>
            <rptOwnerState>OR</rptOwnerState>
            <rptOwnerZipCode>97205</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock / $1.00 Par Value</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2005-08-10</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>135.614</value>
                    <footnoteId id="F2"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>61.9405</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7701.7934</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock / $1.00 Par Value</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2005-08-10</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>7701.7934</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F3"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Pursuant to the Agreement and Plan of Merger among Unocal Corporation, Chevron Corporation and Blue Merger Sub Inc. (the &quot;Merger Agreement&quot;), each share of Unocal Corporation Common Stock issued and outstanding immediately prior to the effectiveness of the merger on August 10, 2005 (the &quot;Merger&quot;), together with the Preferred Stock Purchase Rights attached thereto, was converted into the right to receive the merger consideration specified in the Merger Agreement.</footnote>
        <footnote id="F2">Stock Units credited for voluntary deferral of director
fees under the 2004 Directors' Deferred Compensation and
Restricted Stock Unit Award Plan (the &quot;Directors' Plan&quot;).</footnote>
        <footnote id="F3">In connection with the Merger, each of the 7,701.7934 Director Stock Units owned by the reporting person under the Directors' Plan was converted into Chevron Shares or Chevron Director Stock Units, depending on the reporting person's distribution elections, at the ratio of 1.068831 Chevron shares or units for each Unocal Stock Unit.  The closing price of Chevron Common Stock on August 10, 2005 was $62.48</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Paul R. Moore, Asst Secretary, Attorney-In-Fact</signatureName>
        <signatureDate>2005-08-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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