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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 OEH5duq7k7KelI5yOVaLwQ==

<SEC-DOCUMENT>0001140361-09-029632.txt : 20091217
<SEC-HEADER>0001140361-09-029632.hdr.sgml : 20091217
<ACCEPTANCE-DATETIME>20091217194859
ACCESSION NUMBER:		0001140361-09-029632
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20091216
FILED AS OF DATE:		20091217
DATE AS OF CHANGE:		20091217

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Nielsen Robert R
		CENTRAL INDEX KEY:			0001360998

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-34474
		FILM NUMBER:		091248368

	MAIL ADDRESS:	
		STREET 1:		C/O CENTURY ALUMINUM COMPANY
		STREET 2:		2511 GARDEN ROAD, BLDG. A, SUITE 200
		CITY:			MONTEREY
		STATE:			CA
		ZIP:			93940

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			CENTURY ALUMINUM CO
		CENTRAL INDEX KEY:			0000949157
		STANDARD INDUSTRIAL CLASSIFICATION:	PRIMARY PRODUCTION OF ALUMINUM [3334]
		IRS NUMBER:				133070826
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		2511 GARDEN ROAD
		STREET 2:		BUILDING A SUITE 200
		CITY:			MONTEREY
		STATE:			CA
		ZIP:			93940
		BUSINESS PHONE:		3042736000

	MAIL ADDRESS:	
		STREET 1:		2511 GARDEN ROAD
		STREET 2:		BUILDING A SUITE 200
		CITY:			MONTEREY
		STATE:			CA
		ZIP:			93940
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc1.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-12-16</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000949157</issuerCik>
        <issuerName>CENTURY ALUMINUM CO</issuerName>
        <issuerTradingSymbol>CENX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001360998</rptOwnerCik>
            <rptOwnerName>Nielsen Robert R</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>CENTURY ALUMINUM COMPANY</rptOwnerStreet1>
            <rptOwnerStreet2>2511 GARDEN ROAD, BLDG. A, SUITE 200</rptOwnerStreet2>
            <rptOwnerCity>MONTEREY</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>93940</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Vice President</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2009-12-16</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>42767</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.12</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2460</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>176.4855</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>401(k) Plan</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Represents the average sale price of 42,767 shares in multiple transactions at prices ranging from $14.0884 to $14.17, resulting in a weighted average sale price of $14.12.  Upon the request of the Securities and Exchange Commission (SEC), the Reporting Person will provide the SEC with full information regarding the number of shares and prices at which the transactions were effected.</footnote>
        <footnote id="F2">Includes unvested shares of performance share units granted to the Reporting Person in connection with the Issuer's 2008-2010 Performance Program Period under a Rule 16b-3(d) plan, all of which vest in the ordinary course on December 31, 2010, or earlier, upon the Reporting Person's termination of employment with the Issuer and its subsidiaries due to death, disability, termination other than for cause or other reason approved by the Compensation Committee of the Issuer's Board of Directors.</footnote>
        <footnote id="F3">Reported by 401(k) plan trustee on December 15, 2009.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>William J. Leatherberry, Attorney-in-Fact for Robert R. Nielsen</signatureName>
        <signatureDate>2009-12-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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