-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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<SEC-DOCUMENT>0000007332-05-000072.txt : 20050617
<SEC-HEADER>0000007332-05-000072.hdr.sgml : 20050617
<ACCEPTANCE-DATETIME>20050617182320
ACCESSION NUMBER:		0000007332-05-000072
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050616
FILED AS OF DATE:		20050617
DATE AS OF CHANGE:		20050617

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			SOUTHWESTERN ENERGY CO
		CENTRAL INDEX KEY:			0000007332
		STANDARD INDUSTRIAL CLASSIFICATION:	CRUDE PETROLEUM & NATURAL GAS [1311]
		IRS NUMBER:				710205415
		STATE OF INCORPORATION:			AR
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		2350 N. SAM HOUSTON PARKWAY EAST
		STREET 2:		SUITE 300
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77032
		BUSINESS PHONE:		2816184700

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ARKANSAS WESTERN GAS CO
		DATE OF NAME CHANGE:	19790917

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			WILSON STANLEY T
		CENTRAL INDEX KEY:			0001103815

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-08246
		FILM NUMBER:		05904131

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		2816184700

	MAIL ADDRESS:	
		STREET 1:		2350 N. SAM HOUSTON PARKWAY EAST
		STREET 2:		SUITE 300
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77032
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>c0001103815d20050617f4f.xml
<DESCRIPTION>PRIMARY DOCUMENT
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<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-06-16</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000007332</issuerCik>
        <issuerName>SOUTHWESTERN ENERGY CO</issuerName>
        <issuerTradingSymbol>SWN</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001103815</rptOwnerCik>
            <rptOwnerName>WILSON STANLEY T</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2350 N. SAM HOUSTON PARKWAY EAST</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 300</rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77032</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Accounting Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

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            <deemedExecutionDate></deemedExecutionDate>
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            <transactionAmounts>
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                </transactionShares>
                <transactionPricePerShare>
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                <transactionPricePerShare>
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            <transactionTimeliness>
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                </transactionShares>
                <transactionPricePerShare>
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                <transactionAcquiredDisposedCode>
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            <transactionDate>
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    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Options (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.82</value>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2005-06-16</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
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            <transactionAmounts>
                <transactionShares>
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                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2002-12-20</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-12-20</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
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                </underlyingSecurityTitle>
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                    <value>127</value>
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                <transactionPricePerShare>
                    <value>0</value>
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                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
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                    <value>3426</value>
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                <directOrIndirectOwnership>
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                <value>2005-06-16</value>
            </transactionDate>
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                    <value>400</value>
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                <transactionPricePerShare>
                    <value>0</value>
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                <transactionAcquiredDisposedCode>
                    <value>D</value>
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                <value>2004-12-10</value>
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                <value>2013-12-10</value>
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                    <footnoteId id="F4"/>
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                <sharesOwnedFollowingTransaction>
                    <value>3026</value>
                </sharesOwnedFollowingTransaction>
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    </derivativeTable>

    <footnotes>
        <footnote id="F1">On May 20, 2005, the common stock of Southwestern Energy Company split 2-for-1, resulting in the reporting person's acquisition of 14,334 additional shares of common stock.</footnote>
        <footnote id="F2">This option was previously reported as covering 1,800 shares at an exercise price of $9.64, but was adjusted to reflect the stock split on May 20, 2005.</footnote>
        <footnote id="F3">This option was previously reported as covering 3,470 shares at an exercise price of $11.46 per share, but was adjusted to reflect the stock split on May 20, 2005.</footnote>
        <footnote id="F4">This option was previously reported as covering 2,270 shares at an exercise price of $21.14 per share, but was adjusted to reflect the stock split on May 20, 2005.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Melissa D. McCarty,  Attorney-in-Fact</signatureName>
        <signatureDate>2005-06-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----