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Filed Pursuant to Rule 424(b)(5)
Registration No. 333-208074

The information in this prospectus supplement is not complete and may be changed. This prospectus supplement and the accompanying prospectus are part of an effective registration statement filed with the Securities and Exchange Commission. This prospectus supplement and the accompanying prospectus are not an offer to sell these securities and we are not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

Subject to Completion

Preliminary Prospectus Supplement dated June 29, 2016

PROSPECTUS SUPPLEMENT

(To prospectus dated November 17, 2015)

75,000,000 Shares

Southwestern Energy Company

Common Stock

We are offering 75,000,000 shares of our common stock, par value $0.01 per share.

The underwriters have agreed to purchase the shares of common stock from us at a price of $         per share, which will result in $         million of net proceeds to us before expenses. The underwriters may offer the common stock from time to time for sale in one or more transactions on the New York Stock Exchange (“NYSE”) in the over-the-counter market, through negotiated transactions or otherwise at market prices prevailing at the time of sale, at prices related to prevailing market prices or at negotiated prices.

Our common stock is listed on the NYSE under the symbol “SWN.” The last reported sale price of our common stock on the NYSE on June 28, 2016 was $13.89 per share.

The underwriters have the option to purchase up to an additional 11,250,000 shares of our common stock on the same terms and conditions as set forth herein, within 30 days from the date of this prospectus supplement.

Investing in our common stock involves risks. See “Risk Factors” on page S-7 and the risk factors incorporated by reference in this prospectus supplement and the accompanying base prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying base prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the shares to investors on or about June     , 2016.

Book-Running Manager

Credit Suisse

The date of this prospectus supplement is June     , 2016.

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PROSPECTUS SUPPLEMENT

PROSPECTUS

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ABOUT THIS PROSPECTUS SUPPLEMENT

This document is in two parts. The first part is the prospectus supplement, which describes the specific terms of this offering. The second part, the accompanying prospectus, including the documents incorporated by reference, provides more general information, some of which may not apply to this offering. The accompanying prospectus was filed as part of our registration statement on Form S-3 (Registration No. 333-208074) with the Securities and Exchange Commission (the “SEC”) on November 17, 2015 as part of a “shelf” registration process. Under the shelf registration process, we may offer to sell debt securities, preferred or common stock and guarantees of debt securities, from time to time, in one or more offerings in an unlimited amount. Generally, when we refer to this prospectus supplement, we are referring to both parts of this document combined. We urge you to read carefully this prospectus supplement, the information incorporated by reference, the accompanying prospectus, and any free writing prospectus that we authorize to be distributed to you before buying any of the securities being offered under this prospectus supplement. This prospectus supplement may supplement, update or change information contained in the accompanying prospectus. To the extent that any statement that we make in this prospectus supplement is inconsistent with statements made in the accompanying prospectus or any documents incorporated by reference therein, the statements made in this prospectus supplement will be deemed to modify or supersede those made in the accompanying prospectus and such documents incorporated by reference therein.

Neither we nor the underwriters have authorized anyone to provide you with information that is different from that contained or incorporated by reference in this prospectus or in any free writing prospectus we may authorize to be delivered or made available to you. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. If information in this prospectus supplement is inconsistent with the accompanying prospectus, you should rely on this prospectus supplement. We are not, and the underwriters are not, making an offer of these securities in any state where the offer or sale is not permitted. You should not assume that the information provided by this prospectus supplement, the accompanying prospectus or the documents incorporated by reference in this prospectus supplement and in the accompanying prospectus is accurate as of any date other than their respective dates. Our business, financial condition, results of operations and prospects may have changed since those dates.

Before you invest in our common stock, you should carefully read the registration statement described in the accompanying prospectus (including the exhibits thereto) of which this prospectus supplement and the accompanying prospectus form a part, as well as this prospectus supplement, the accompanying prospectus and the documents incorporated by reference into this prospectus supplement and the accompanying prospectus. The incorporated documents are described in this prospectus supplement under “Incorporation by Reference.”

Unless otherwise indicated or the context otherwise requires, all references to “Southwestern,” “the Company,” “we,” “us” and “our” in this prospectus supplement refer to Southwestern Energy Company and its direct and indirect subsidiaries on a consolidated basis.

INCORPORATION BY REFERENCE

The SEC allows us to “incorporate by reference” the information that we file with it, which means that we can disclose important information to you by referring you to other documents. The information incorporated by reference is an important part of this prospectus supplement, and information that we file later with the SEC will automatically update and supersede this information. We incorporate by reference the following documents and all documents that we subsequently file with the SEC under Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”) (other than the portions of those documents furnished under Item 2.02 or Item 7.01 and related exhibits thereto):

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FORWARD-LOOKING STATEMENTS

Certain statements and information in this prospectus supplement, the accompanying base prospectus and the documents incorporated by reference herein and therein may constitute “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. The words “believe,” “expect,” “anticipate,” “plan,” “intend,” “foresee,” “should,” “would,” “could,” “attempt,” “appears,” “forecast,” “outlook,” “estimate,” “project,” “potential,” “may,” “will,” “are likely” and other similar expressions are intended to identify forward-looking statements, which are generally not historical in nature. These forward-looking statements are based on our current expectations and beliefs concerning future developments and their potential effect on us.

The forward-looking statements contained in this document are largely based on our expectations for the future, which reflect certain estimates and assumptions made by our management. These estimates and assumptions reflect our best judgment based on currently known market conditions, operating trends, and other factors. Although we believe such estimates and assumptions to be reasonable, they are inherently uncertain and involve a number of risks and uncertainties that are beyond our control. As such, management’s assumptions about future events may prove to be inaccurate. For a more detailed description of the risks and uncertainties involved, see “Risk Factors” beginning on page S-7 of this prospectus supplement and on page 5 of the accompanying prospectus, as well as “Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2015. We do not intend to publicly update or revise any forward-looking statements as a result of new information, future events, changes in circumstances, or otherwise. These cautionary statements qualify all forward-looking statements attributable to us, or persons acting on our behalf. Management cautions you that the forward-looking statements contained in this prospectus supplement, the accompanying prospectus or the documents incorporated by reference herein and therein are not guarantees of future performance, and we cannot assure you that such statements will be realized or that the events and circumstances they describe will occur. Factors that could cause actual results to differ materially from those anticipated or implied in the forward-looking statements herein include, but are not limited to:

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All written and oral forward-looking statements attributable to us are expressly qualified in their entirety by this cautionary statement. For additional information with respect to these factors, see “Incorporation by Reference.”

MARKET AND INDUSTRY DATA

Market and industry data and forecasts included or incorporated by reference in this prospectus supplement have been obtained from independent industry sources as well as from research reports prepared for other purposes. Although we believe these third-party sources to be reliable, we have not independently verified the data obtained from these sources and we cannot assure you of the accuracy or completeness of the data. Forecasts and other forward-looking information obtained from these sources are subject to the same qualifications and uncertainties as the other forward-looking statements included or incorporated by reference in this prospectus supplement.

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RISK FACTORS

An investment in our common stock involves risks. You should consider carefully the following risks, as well as the risk factors discussed under the caption “Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2015, and our subsequent Quarterly Reports on Form 10-Q together with all of the other information included in, or incorporated by reference into, this prospectus supplement and the accompanying prospectus, when evaluating an investment in our common stock.

Risks Relating to the Offering and our Common Stock

The market price of our common stock may be volatile or may decline and it may be difficult for you to resell shares of our common stock at prices you find attractive.

The market price of our common stock has historically experienced and may continue to experience volatility. For example, during the last twelve months, the high sales price per share of our common stock on the NYSE was $23.43 and the low sales price per share was $5.00. The price of our common stock could be subject to wide fluctuations in the future in response to the following events or factors:

In particular, a significant or extended decline in natural gas and oil prices would have a material adverse effect on our financial position, our results of operations, our access to capital and the quantities of natural gas and oil that we can produce economically. For example, during the last twelve months, natural gas prices on the New York Mercantile Exchange (“NYMEX”), traded at a high of $2.93 on August 12, 2015 and a low of $1.64 on March 3, 2016 based on last day of month settlements. Other risks described elsewhere under “Risk Factors” in this prospectus supplement and the accompanying prospectus and in the documents incorporated by reference in this prospectus supplement also could materially and adversely affect our share price.

The availability of our common stock for sale in the future could reduce the market price of our common stock.

Except as described herein under “Underwriting,” we are not restricted from issuing additional common stock, including securities that are convertible into or exchangeable for, or that represent the right to receive, common stock, including any common stock that may be issued upon the conversion of our mandatory convertible preferred stock (and, correspondingly, our depositary shares). In the future, we may sell additional shares of our common stock to raise capital or acquire interests in other companies by using a combination of cash and our common stock or just our common stock. Any of these events may dilute your ownership interest in our company and have an adverse impact on the price of our common stock. In addition, a substantial number of

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+shares of our common stock are reserved for issuance as payment for dividends on our mandatory convertible preferred stock, upon the exercise of stock options and upon conversion of our mandatory convertible preferred stock. Sales of a substantial number of shares of our common stock could depress the market price of our common stock and impair our ability to raise capital through the sale of additional equity securities. We cannot predict the effect that future sales of our common stock, or the perception that these sales may occur, or other equity-related securities would have on the market price of our common stock.

Purchasers in this offering will experience immediate dilution. If you purchase shares of common stock in this offering, you will pay more for your shares than the per share book value as of March 31, 2016.

Our mandatory convertible preferred stock and the depositary shares may adversely affect the market price of our common stock.

The market price of our common stock is likely to be influenced by our mandatory convertible preferred stock and depositary shares. For example, the market price of our common stock could become more volatile and could be depressed by:

Because we have no plans to pay dividends on our common stock, investors must look solely to stock appreciation for a return on their investment in us.

We do not currently pay cash dividends on our capital stock, and we do not anticipate paying cash dividends in the foreseeable future. We currently intend to retain all future earnings and other cash resources, if any, for the operation and development of our business and do not anticipate paying cash dividends in the foreseeable future. Payment of any future dividends will be at the discretion of our board of directors after taking into account many factors, including our financial condition, operating results, current and anticipated cash needs and plans for expansions. Any future dividends may also be restricted by any loan agreements which we may enter into from time to time and from the issuance of preferred stock should we decide to do so in the future.

Anti-takeover provisions in our organizational documents and under Delaware law may impede or discourage a takeover, which could cause the market price of our common stock to decline.

We are a Delaware corporation, and the anti-takeover provisions of Delaware law impose various impediments to the ability of a third party to acquire control of us, even if a change in control would be beneficial to our existing stockholders, which, under certain circumstances, could reduce the market price of our common stock. In addition, protective provisions in our Amended and Restated Certificate of Incorporation and Amended and Restated Bylaws or the implementation by our board of directors of a stockholder rights plan could prevent a takeover, which could harm our stockholders.

We may not consummate the Tender Offers, and this offering is not conditioned on the consummation of the Tender Offers.

We intend to use $750 million of the net proceeds from this offering to fund the Tender Offers, as described under “Summary—Recent Developments—Tender Offers for Senior Notes.” However, there can be no assurance as to the amount of Target Notes that will be tendered in the Tender Offers or that we will consummate the Tender Offers, which are subject to market conditions and other factors. This offering is not conditioned on

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the consummation of the Tender Offers. Therefore, upon the closing of this offering, you will become a holder of our common stock regardless of whether the Tender Offers are consummated, delayed or terminated. If the Tender Offers are delayed or terminated, the value of our common stock may decline to the extent that their price reflects a market assumption that the Tender Offers will be consummated on the terms described herein. If the Tender Offers are not consummated, we may use such proceeds for general corporate purposes (see “Use of Proceeds”).

Certain U.S. federal income tax deductions currently available with respect to oil and natural gas exploration and production may be eliminated as a result of future legislation.

The elimination of certain key U.S. federal income tax deductions currently available to oil and natural gas exploration and production companies has been proposed in recent years by members of the U.S. Congress and by the President in his fiscal year 2017 budget proposal. These changes have included, among other proposals:

In addition, the President’s fiscal year 2017 budget proposal includes the imposition of a new $10.25 per barrel fee on certain oil production, to be paid by certain oil companies (without precise details regarding the implementation of such fee). It is unclear whether these or similar changes will be enacted. The passage of these or any similar changes in U.S. federal income tax laws to eliminate or postpone certain tax deductions that are currently available with respect to oil and natural gas exploration and development could have an adverse effect on our financial position, results of operations and cash flows.

Our current and future levels of indebtedness may adversely affect our results and limit our growth.

As of March 31, 2016, as adjusted to give effect to (i) the April 1, 2016 repayment of approximately $1.55 billion of borrowings incurred under our revolving credit facility on March 31, 2016 and outstanding as of that date and (ii) the transactions described above under “Summary—Recent Developments—Credit Facility Amendments,” in each case as if such event occurred on March 31, 2016, we had long-term indebtedness of $5.406 billion, including $1.191 billion (our New Term Loan) and approximately $169 million of letters of credit under the New Credit Agreements and no borrowings under the 2013 Credit Agreement. The terms of the indentures relating to our outstanding senior notes, our credit facilities, and the master lease agreements relating to our drilling rigs and other equipment, which we collectively refer to as our “financing agreements,” impose restrictions on our ability and, in some cases, the ability of our subsidiaries to take a number of actions that we may otherwise desire to take, which may include, without limitation, one or more of the following:

Under the 2013 Credit Agreement, we must keep our total debt at or below 60% of our total adjusted book capital. This financial covenant with respect to capitalization percentages excludes the effects of any non-cash impacts from any full cost ceiling impairments, certain non-cash hedging activities and our pension and other

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postretirement liabilities. Therefore, under the 2013 Credit Agreement, our adjusted capital structure as of March 31, 2016 was 45% debt and 55% equity. Under our New Credit Agreements, we must maintain certain covenants, including, among others, the following financial covenants:

Although we do not anticipate any violations of our financial covenants, our ability to comply with these covenants are dependent upon the success of our exploration and development program and upon factors beyond our control, such as the market prices for natural gas, oil and NGLs.

Although the indentures governing our outstanding notes contain covenants limiting liens and sale and leaseback transactions, these covenants contain exceptions that would allow us to create, grant or incur certain liens or security interests. Moreover, the indentures do not contain any limitations on the ability of us or our subsidiaries to incur debt, pay dividends or make investments, or limit the ability of our subsidiaries to make distributions to us. Such activities may, however, be limited by our other financing agreements in certain circumstances.

Our level of indebtedness and off-balance sheet obligations, and the covenants contained in our financing agreements, could have important consequences for our operations, including:

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USE OF PROCEEDS

We expect to receive net proceeds from this offering of approximately $             million, or $             million if the underwriters exercise their option to purchase additional shares of common stock in full, after deducting estimated offering expenses. We intend to use $375 million of the net proceeds to reduce our outstanding indebtedness under the 2015 Term Loan and the remaining net proceeds of this offering, together with cash on hand, to fund the Tender Offers. If the Tender Offers are not consummated, or the aggregate amount of securities tendered in the Tender Offers and accepted for payment is less than the net proceeds of this offering dedicated for that purpose, we will use the remainder of those proceeds to repay or retire other outstanding indebtedness, including additional indebtedness outstanding under the 2015 Term Loan, and for general corporate purposes, including the repayment of additional indebtedness outstanding under the 2015 Term Loan, the completion of wells already drilled or the funding of other capital projects. Until we apply the net proceeds for the purposes described above with respect to the Tender Offers, we may invest them in short-term, liquid investments. The net proceeds from any exercise by the underwriters of their option to purchase additional shares of common stock from us will be used to fund a portion of the Tender Offers or for general corporate purposes as described above. For a more detailed discussion of the Tender Offers and the funding of the additional capital projects read “Summary—Recent Developments—Asset Sales” and “—Capital Expenditures Budget.”

As of June 28, 2016, we had $750.0 million of borrowings outstanding under the 2015 Term Loan. The weighted average interest rate on the total amount outstanding at June 28, 2016 was 2.93%. The 2015 Term Loan has an initial maturity date of November 17, 2018. We used borrowings under the 2015 Term Loan to for general corporate purposes.

As of June 28, 2016, we had $350.0 million in aggregate principal amount of the 3.30% Notes outstanding, $600.0 million in aggregate principal amount of the 7.50% Notes outstanding and $850.0 million in aggregate principal amount of the 4.05% Notes outstanding.

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CAPITALIZATION

The following table sets forth our cash and cash equivalents and capitalization as of March 31, 2016:

The following table does not give effect to the Tender Offers. See “Summary—Recent Developments—Tender Offers for Senior Notes.”

You should read our historical consolidated financial statements and notes that are incorporated by reference into this prospectus supplement.

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DIVIDEND POLICY AND MARKET FOR COMMON STOCK

Dividend Policy

We do not currently pay cash dividends on our capital stock, and we do not anticipate paying cash dividends in the foreseeable future. Holders of our common stock may receive dividends when, as and if declared by our board of directors out of funds lawfully available for the payment of dividends. As a Delaware corporation, we may pay dividends out of surplus or, if there is no surplus, out of net profits for the fiscal year in which a dividend is declared and/or the preceding fiscal year. Section 170 of the Delaware General Corporation Law also provides that dividends may not be paid out of net profits if, after the payment of the dividend, capital is less than the capital represented by the outstanding stock of all classes having a preference upon the distribution of assets.

Price Range of Our Common Stock

The following table sets forth the high and low sales prices per share of our common stock as reported on the NYSE since January 1, 2014.

As of June 23, 2016, there were 3,371 holders of record of our common stock.

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U.S. FEDERAL INCOME TAX CONSIDERATIONS TO NON-U.S. HOLDERS

The following discussion is a summary of the material U.S. federal income tax consequences to Non-U.S. Holders (as defined below) of the purchase, ownership and disposition of our common stock issued pursuant to this offering, but does not purport to be a complete analysis of all potential tax effects. The effects of other U.S. federal tax laws, such as estate and gift tax laws, and any applicable state, local or non-U.S. tax laws are not discussed. This discussion is based on the U.S. Internal Revenue Code of 1986, as amended (the “Code”), Treasury regulations promulgated thereunder (“Treasury Regulations”), judicial decisions, and published rulings and administrative pronouncements of the U.S. Internal Revenue Service (the “IRS”), in each case as in effect as of the date hereof. These authorities may change or be subject to differing interpretations. Any such change or differing interpretation may be applied retroactively in a manner that could adversely affect a Non-U.S. Holder of our common stock. We have not sought and will not seek any rulings from the IRS regarding the matters discussed below. There can be no assurance the IRS or a court will not take a contrary position to those discussed below regarding the tax consequences of the purchase, ownership and disposition of our common stock.

This discussion is limited to Non-U.S. Holders that hold our common stock as a “capital asset” within the meaning of Section 1221 of the Code (generally, property held for investment). This discussion does not address all U.S. federal income tax consequences relevant to a Non-U.S. Holder’s particular circumstances, including the impact of the Medicare contribution tax on net investment income. In addition, it does not address consequences relevant to Non-U.S. Holders subject to special rules, including, without limitation:

If an entity treated as a partnership for U.S. federal income tax purposes holds our common stock, the tax treatment of a partner in the partnership will depend on the status of the partner, the activities of the partnership and certain determinations made at the partner level. Accordingly, partnerships holding our common stock and partners in such partnerships should consult their tax advisors regarding the U.S. federal income tax consequences to them.

THIS DISCUSSION IS FOR INFORMATIONAL PURPOSES ONLY AND IS NOT TAX ADVICE. INVESTORS SHOULD CONSULT THEIR TAX ADVISORS WITH RESPECT TO THE APPLICATION OF THE U.S. FEDERAL INCOME TAX LAWS TO THEIR PARTICULAR SITUATIONS AS WELL AS ANY TAX CONSEQUENCES OF THE PURCHASE, OWNERSHIP AND

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DISPOSITION OF OUR COMMON STOCK ARISING UNDER THE U.S. FEDERAL ESTATE OR GIFT TAX LAWS OR UNDER THE LAWS OF ANY STATE, LOCAL OR NON-U.S. TAXING JURISDICTION OR UNDER ANY APPLICABLE INCOME TAX TREATY.

Definition of a Non-U.S. Holder

For purposes of this discussion, a “Non-U.S. Holder” is any beneficial owner of our common stock that is neither a “U.S. person” nor an entity treated as a partnership for U.S. federal income tax purposes. A U.S. person is any person that, for U.S. federal income tax purposes, is or is treated as any of the following:

Distributions

As described in the section entitled “Dividend Policy and Market for Common Stock—Dividend Policy,” we do not anticipate declaring or paying dividends to holders of our common stock in the foreseeable future. However, if we do make distributions of cash or property on our common stock, such distributions will constitute dividends for U.S. federal income tax purposes to the extent paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. Amounts not treated as dividends for U.S. federal income tax purposes will constitute a return of capital and first be applied against and reduce a Non-U.S. Holder’s adjusted tax basis in its common stock, but not below zero. Any excess will be treated as capital gain and will be treated as described below under “—Sale or Other Taxable Disposition.”

Subject to the discussion below on effectively connected income, dividends paid to a Non-U.S. Holder of our common stock will be subject to U.S. federal withholding tax at a rate of 30% of the gross amount of the dividends (or such lower rate specified by an applicable income tax treaty, provided the Non-U.S. Holder furnishes a valid IRS Form W-8BEN or W-8BEN-E (or other applicable documentation) certifying qualification for the lower treaty rate). A Non-U.S. Holder that does not timely furnish the required documentation, but that qualifies for a reduced treaty rate, may obtain a refund of any excess amounts withheld by timely filing an appropriate claim for refund with the IRS. Non-U.S. Holders should consult their tax advisors regarding their entitlement to benefits under any applicable income tax treaty.

If dividends paid to a Non-U.S. Holder are effectively connected with the Non-U.S. Holder’s conduct of a trade or business within the United States (and, if required by an applicable income tax treaty, the Non-U.S. Holder maintains a permanent establishment in the United States to which such dividends are attributable), the Non-U.S. Holder will be exempt from the U.S. federal withholding tax described above. To claim the exemption, the Non-U.S. Holder must furnish to the applicable withholding agent a valid IRS Form W-8ECI, certifying that the dividends are effectively connected with the Non-U.S. Holder’s conduct of a trade or business within the United States.

Any such effectively connected dividends will be subject to U.S. federal income tax on a net income basis at the regular graduated rates. A Non-U.S. Holder that is a corporation also may be subject to a branch profits tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on its effectively connected earnings and profits (as adjusted for certain items), which will include such effectively connected dividends. Non-U.S. Holders should consult their tax advisors regarding any applicable tax treaties that may provide for different rules.

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Sale or Other Taxable Disposition

A Non-U.S. Holder will not be subject to U.S. federal income tax on any gain realized upon the sale or other taxable disposition of our common stock unless:

Gain described in the first bullet point above generally will be subject to U.S. federal income tax on a net income basis at the regular graduated rates. A Non-U.S. Holder that is a corporation also may be subject to a branch profits tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on its effectively connected earnings and profits (as adjusted for certain items), which will include such effectively connected gain.

A Non-U.S. Holder described in the second bullet point above will be subject to U.S. federal income tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on any gain derived from the disposition, which may be offset by U.S. source capital losses of the Non-U.S. Holder (even though the individual is not considered a resident of the United States), provided the Non-U.S. Holder has timely filed U.S. federal income tax returns with respect to such losses.

With respect to the third bullet point above, we believe that we currently are, and expect to remain for the foreseeable future, a USRPHC for U.S. federal income tax purposes. However, so long as our common stock is “regularly traded on an established securities market,” a Non-U.S. Holder will be subject to U.S. federal net income tax on a disposition of our common stock only if the Non-U.S. Holder actually or constructively holds or held (at any time during the shorter of the five-year period preceding the date of disposition or the Non-U.S. Holder’s holding period) more than 5% of our common stock. If our common stock is not considered to be regularly traded on an established securities market during the calendar year in which the relevant disposition by a Non-U.S. Holder occurs, such holder (regardless of the percentage of stock owned) generally would be subject to U.S. federal income tax on the gain realized on a disposition of our common stock and generally would be required to file a U.S. federal income tax return, and a 15% withholding tax would apply to the gross proceeds from such sale.

Non-U.S. Holders should also consult their tax advisors (i) with respect to the application of the foregoing rules to their ownership and disposition of our common stock and (ii) regarding potentially applicable income tax treaties that may provide for different rules.

Information Reporting and Backup Withholding

Payments of dividends on our common stock will not be subject to backup withholding, provided the applicable withholding agent does not have actual knowledge or reason to know the Non-U.S. Holder is a United States person and the Non-U.S. Holder either certifies its non-U.S. status, such as by furnishing a valid IRS Form W-8BEN, W-8BEN-E or W-8ECI, or otherwise establishes an exemption. However, information returns are required to be filed with the IRS in connection with any dividends on our common stock paid to the Non-U.S.

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Holder, regardless of whether any tax was actually withheld. In addition, proceeds of the sale or other taxable disposition of our common stock within the United States or conducted through certain U.S.-related brokers generally will not be subject to backup withholding or information reporting if the applicable withholding agent receives the certification described above and does not have actual knowledge or reason to know that such Non-U.S. Holder is a United States person, or the Non-U.S. Holder otherwise establishes an exemption. Proceeds of a disposition of our common stock conducted through a non-U.S. office of a non-U.S. broker generally will not be subject to backup withholding or information reporting.

Copies of information returns that are filed with the IRS may also be made available under the provisions of an applicable treaty or agreement to the tax authorities of the country in which the Non-U.S. Holder resides or is established.

Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules may be allowed as a refund or a credit against a Non-U.S. Holder’s U.S. federal income tax liability, provided the required information is timely furnished to the IRS.

Additional Withholding Tax on Payments Made to Foreign Accounts

Withholding taxes may be imposed under Sections 1471 to 1474 of the Code (such Sections commonly referred to as the Foreign Account Tax Compliance Act, or “FATCA”) on certain types of payments made to non-U.S. financial institutions and certain other non-U.S. entities. Specifically, a 30% withholding tax may be imposed on dividends on, or gross proceeds from the sale or other disposition of, our common stock paid to a “foreign financial institution” or a “non-financial foreign entity” (each as defined in the Code) (including in some cases when such foreign financial institutions or non-financial foreign entity is acting as an intermediary), unless (1) the foreign financial institution undertakes certain diligence and reporting obligations, (2) the non-financial foreign entity either certifies it does not have any “substantial United States owners” (as defined in the Code) or furnishes identifying information regarding each direct and indirect substantial United States owner, or (3) the foreign financial institution or non-financial foreign entity otherwise qualifies for an exemption from these rules and provides appropriate documentation (such as IRS Form W-8BEN-E). If the payee is a foreign financial institution and is subject to the diligence and reporting requirements in (1) above, it must enter into an agreement with the U.S. Department of the Treasury requiring, among other things, that it undertake to identify accounts held by certain “specified United States persons” or “United States-owned foreign entities” (each as defined in the Code), annually report certain information about such accounts, and withhold 30% on certain payments to non-compliant foreign financial institutions and certain other account holders. Foreign financial institutions located in jurisdictions that have an intergovernmental agreement with the United States governing FATCA may be subject to different rules.

Under the applicable Treasury Regulations and administrative guidance, withholding under FATCA generally applies to payments of dividends on our common stock, and will apply to payments of gross proceeds from the sale or other disposition of such stock on or after January 1, 2019.

Prospective investors should consult their tax advisors regarding the potential application of withholding under FATCA to their investment in our common stock.

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UNDERWRITING

Credit Suisse Securities (USA) LLC is acting as representative of each of the underwriters named below. Subject to the terms and conditions set forth in an underwriting agreement among us and the underwriters, we have agreed to sell to the underwriters, and each of the underwriters has agreed, severally and not jointly, to purchase from us, the number of shares of common stock set forth opposite its name below.

Subject to the terms and conditions set forth in the underwriting agreement, the underwriters have agreed, severally and not jointly, to purchase all of the shares sold under the underwriting agreement if any of these shares are purchased. If an underwriter defaults, the underwriting agreement provides that the purchase commitments of the nondefaulting underwriters may be increased or the underwriting agreement may be terminated.

We have agreed to indemnify the underwriters against certain liabilities, including liabilities under the Securities Act, or to contribute to payments the underwriters may be required to make in respect of those liabilities.

The underwriters are offering the shares, subject to prior sale, when, as and if issued to and accepted by them, subject to approval of legal matters by their counsel, including the validity of the shares, and other conditions contained in the underwriting agreement, such as the receipt by the underwriters of officer’s certificates and legal opinions. The underwriters reserve the right to withdraw, cancel or modify offers to the public and to reject orders in whole or in part.

Commissions and Discounts

The underwriters may receive from purchasers of the common stock normal brokerage commissions in amounts agreed with such purchasers. The underwriters may offer the common stock from time to time for sale in one or more transactions on the NYSE, in the over-the-counter market, through negotiated transactions or otherwise at market prices prevailing at the time of sale, at prices related to prevailing market prices or at negotiated prices, subject to receipt and acceptance by it and subject to its right to reject any order in whole or in part. In connection with the sale of the common stock offered hereby, the underwriters may be deemed to have received compensation in the form of underwriting discounts. The underwriters may effect such transactions by selling common stock to or through dealers, and such dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters and/or purchasers of common stock for whom they may act as agents or to whom they may sell as principal.

The expenses of the offering are estimated at $745,000 and are payable by us.

Option to Purchase Additional Shares

We have granted an option to the underwriters, exercisable for 30 days after the date of this prospectus, to purchase up to 11,250,000 additional shares at the public offering price, less the underwriting discount. If the underwriters exercise this option, each will be obligated, subject to conditions contained in the underwriting agreement, to purchase a number of additional shares proportionate to that underwriter’s initial amount reflected in the above table.

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No Sales of Similar Securities

We, our executive officers and directors have agreed not to sell or transfer any common stock or securities convertible into, exchangeable for, exercisable for, or repayable with common stock, for 60 days after the date of this prospectus without first obtaining the written consent of Credit Suisse Securities (USA) LLC. Specifically, we and these other persons have agreed, with certain limited exceptions, not to directly or indirectly:

This lock-up provision applies to common stock and to securities convertible into or exchangeable or exercisable for or repayable with common stock. It also applies to common stock owned now or acquired later by the person executing the agreement or for which the person executing the agreement later acquires the power of disposition. Notwithstanding the above, this lock-up provision will not apply to us with respect to, among other things, (i) the common stock offered hereby, (ii) any shares of our common stock issued by us upon the exercise of an option or warrant or the conversion of a security outstanding on the date hereof and referred to in the accompanying prospectus or in this prospectus supplement, (iii) any shares of our common stock issued or options to purchase our common stock granted pursuant to existing employee benefit plans referred to in the accompanying prospectus or in this prospectus supplement, (iv) any shares of our common stock issued upon conversion of our mandatory convertible preferred stock, (v) any shares of our common stock issued and paid as a dividend on our mandatory convertible preferred stock and (vi) any shares of our common stock issued pursuant to any non-employee director stock plan or dividend reinvestment plan referred to in the accompanying prospectus or in this prospectus supplement. Notwithstanding the above, this lock-up provision will not apply to our directors and officers with respect to, among other things, and subject to certain additional limitations, (i) bona fide gifts, (ii) transfers to any trust for the direct or indirect benefit of our directors and officers or the immediate family of our directors and officers, (iii) distributions to limited partners or stockholders of such person or (iv) transfers to our directors’ and officers’ affiliates or to any investment fund or other entity controlled or managed by our directors and officers.

New York Stock Exchange Listing

The shares are listed on the NYSE under the symbol “SWN.”

Price Stabilization, Short Positions

In connection with this offering the underwriters may engage in stabilizing transactions, over-allotment transactions, syndicate covering transactions, penalty bids and passive market making in accordance with Regulation M under the Exchange Act.

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Neither we nor the underwriters make any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the price of our common stock. In addition, neither we nor the underwriters make any representation that the underwriters will engage in these transactions or that these transactions, once commenced, will not be discontinued without notice.

Electronic Distribution

In connection with the offering, certain of the underwriters or securities dealers may distribute prospectuses by electronic means, such as e-mail.

Other Relationships

Some of the underwriters and their affiliates have engaged in, and may in the future engage in, investment banking and other commercial dealings in the ordinary course of business with us or our affiliates. They have received, or may in the future receive, customary fees and commissions for these transactions.

In addition, in the ordinary course of their business activities, the underwriters and their affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers. Such investments and securities activities may involve securities and/or instruments of ours or our affiliates. The underwriters and their affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or financial instruments and may hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

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Selling Restrictions

Notice to Prospective Investors in the European Economic Area

In relation to each member state of the European Economic Area, no offer of ordinary shares which are the subject of the offering has been, or will be made to the public in that Member State other than under the following exemptions under the Prospectus Directive:

provided that no such offer of ordinary shares referred to in (a) to (c) above shall result in a requirement for the Company or any Representative to publish a prospectus pursuant to Article 3 of the Prospectus Directive or supplement a prospectus pursuant to Article 16 of the Prospectus Directive.

Each person located in a Member State to whom any offer of ordinary shares is made or who receives any communication in respect of an offer of ordinary shares, or who initially acquires any ordinary shares will be deemed to have represented, warranted, acknowledged and agreed to and with each Representative and the Company that (1) it is a “qualified investor” within the meaning of the law in that Member State implementing Article 2(1)(e) of the Prospectus Directive; and (2) in the case of any ordinary shares acquired by it as a financial intermediary as that term is used in Article 3(2) of the Prospectus Directive, the ordinary shares acquired by it in the offer have not been acquired on behalf of, nor have they been acquired with a view to their offer or resale to, persons in any Member State other than qualified investors, as that term is defined in the Prospectus Directive, or in circumstances in which the prior consent of the Representatives has been given to the offer or resale; or where ordinary shares have been acquired by it on behalf of any persons in any Member State other than qualified investors, the offer of those ordinary shares to it is not treated under the Prospectus Directive as having been made to such persons.

The Company, the Representative and their respective affiliates will rely upon the truth and accuracy of the foregoing representations, acknowledgments and agreements.

This prospectus has been prepared on the basis that any offer of shares in any Member State will be made pursuant to an exemption under the Prospectus Directive from the requirement to publish a prospectus for offers of shares. Accordingly any person making or intending to make an offer in that Member State of shares which are the subject of the offering contemplated in this prospectus may only do so in circumstances in which no obligation arises for the Company or any of the Representatives to publish a prospectus pursuant to Article 3 of the Prospectus Directive in relation to such offer. Neither the Company nor the Representatives have authorized, nor do they authorize, the making of any offer of shares in circumstances in which an obligation arises for the Company or the Representatives to publish a prospectus for such offer.

For the purposes of this provision, the expression an “offer of ordinary shares to the public” in relation to any ordinary shares in any Member State means the communication in any form and by any means of sufficient information on the terms of the offer and the ordinary shares to be offered so as to enable an investor to decide to purchase or subscribe the ordinary shares, as the same may be varied in the that Member State by any measure implementing the Prospectus Directive in that Member State, the expression “Prospectus Directive” means Directive 2003/71/EC (as amended) and includes any relevant implementing measure in each Member State.

Notice to Prospective Investors in the United Kingdom

In addition, in the United Kingdom, this document is being distributed only to, and is directed only at, and any offer subsequently made may only be directed at persons who are “qualified investors” (as defined in the

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Prospectus Directive) (i) who have professional experience in matters relating to investments falling within Article 19 (5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005, as amended (the “Order”) and/or (ii) who are high net worth companies (or persons to whom it may otherwise be lawfully communicated) falling within Article 49(2)(a) to (d) of the Order (all such persons together being referred to as “relevant persons”). This document must not be acted on or relied on in the United Kingdom by persons who are not relevant persons. In the United Kingdom, any investment or investment activity to which this document relates is only available to, and will be engaged in with, relevant persons.

Notice to Prospective Investors in Switzerland

The shares may not be publicly offered in Switzerland and will not be listed on the SIX Swiss Exchange (“SIX”) or on any other stock exchange or regulated trading facility in Switzerland. This document has been prepared without regard to the disclosure standards for issuance prospectuses under art. 652a or art. 1156 of the Swiss Code of Obligations or the disclosure standards for listing prospectuses under art. 27 ff. of the SIX Listing Rules or the listing rules of any other stock exchange or regulated trading facility in Switzerland. Neither this document nor any other offering or marketing material relating to the shares or the offering may be publicly distributed or otherwise made publicly available in Switzerland.

Neither this document nor any other offering or marketing material relating to the offering, the Company, the shares have been or will be filed with or approved by any Swiss regulatory authority. In particular, this document will not be filed with, and the offer of shares will not be supervised by, the Swiss Financial Market Supervisory Authority FINMA (FINMA), and the offer of shares has not been and will not be authorized under the Swiss Federal Act on Collective Investment Schemes (“CISA”). The investor protection afforded to acquirers of interests in collective investment schemes under the CISA does not extend to acquirers of shares.

Notice to Prospective Investors in the Dubai International Financial Centre

This prospectus supplement relates to an Exempt Offer in accordance with the Offered Securities Rules of the Dubai Financial Services Authority (“DFSA”). This prospectus supplement is intended for distribution only to persons of a type specified in the Offered Securities Rules of the DFSA. It must not be delivered to, or relied on by, any other person. The DFSA has no responsibility for reviewing or verifying any documents in connection with Exempt Offers. The DFSA has not approved this prospectus supplement nor taken steps to verify the information set forth herein and has no responsibility for the prospectus supplement. The shares to which this prospectus supplement relates may be illiquid and/or subject to restrictions on their resale. Prospective purchasers of the shares offered should conduct their own due diligence on the shares. If you do not understand the contents of this prospectus supplement you should consult an authorized financial advisor.

Notice to Prospective Investors in Australia

No placement document, prospectus, product disclosure statement or other disclosure document has been lodged with the Australian Securities and Investments Commission (“ASIC”), in relation to the offering. This prospectus does not constitute a prospectus, product disclosure statement or other disclosure document under the Corporations Act 2001 (the “Corporations Act”), and does not purport to include the information required for a prospectus, product disclosure statement or other disclosure document under the Corporations Act.

Any offer in Australia of the shares may only be made to persons (the “Exempt Investors”) who are “sophisticated investors” (within the meaning of section 708(8) of the Corporations Act), “professional investors” (within the meaning of section 708(11) of the Corporations Act) or otherwise pursuant to one or more exemptions contained in section 708 of the Corporations Act so that it is lawful to offer the shares without disclosure to investors under Chapter 6D of the Corporations Act.

The shares applied for by Exempt Investors in Australia must not be offered for sale in Australia in the period of 12 months after the date of allotment under the offering, except in circumstances where disclosure to

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investors under Chapter 6D of the Corporations Act would not be required pursuant to an exemption under section 708 of the Corporations Act or otherwise or where the offer is pursuant to a disclosure document which complies with Chapter 6D of the Corporations Act. Any person acquiring shares must observe such Australian on-sale restrictions.

This prospectus contains general information only and does not take account of the investment objectives, financial situation or particular needs of any particular person. It does not contain any securities recommendations or financial product advice. Before making an investment decision, investors need to consider whether the information in this prospectus is appropriate to their needs, objectives and circumstances, and, if necessary, seek expert advice on those matters.

Notice to Prospective Investors in Hong Kong

The securities have not been offered or sold and will not be offered or sold in Hong Kong, by means of any document, other than (a) to “professional investors” as defined in the Securities and Futures Ordinance (Cap. 571) of Hong Kong and any rules made under that Ordinance; or (b) in other circumstances which do not result in the document being a “prospectus” as defined in the Companies Ordinance (Cap. 32) of Hong Kong or which do not constitute an offer to the public within the meaning of that Ordinance. No advertisement, invitation or document relating to the securities has been or may be issued or has been or may be in the possession of any person for the purposes of issue, whether in Hong Kong or elsewhere, which is directed at, or the contents of which are likely to be accessed or read by, the public of Hong Kong (except if permitted to do so under the securities laws of Hong Kong) other than with respect to securities which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” as defined in the Securities and Futures Ordinance and any rules made under that Ordinance.

Notice to Prospective Investors in Japan

The securities have not been and will not be registered under the Financial Instruments and Exchange Law of Japan (Law No. 25 of 1948, as amended) and, accordingly, will not be offered or sold, directly or indirectly, in Japan, or for the benefit of any Japanese Person or to others for re-offering or resale, directly or indirectly, in Japan or to any Japanese Person, except in compliance with all applicable laws, regulations and ministerial guidelines promulgated by relevant Japanese governmental or regulatory authorities in effect at the relevant time. For the purposes of this paragraph, “Japanese Person” shall mean any person resident in Japan, including any corporation or other entity organized under the laws of Japan.

Notice to Prospective Investors in Singapore

This prospectus has not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, this prospectus and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of Non-CIS Securities may not be circulated or distributed, nor may the Non-CIS Securities be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to persons in Singapore other than (i) to an institutional investor under Section 274 of the Securities and Futures Act, Chapter 289 of Singapore (the “SFA”), (ii) to a relevant person pursuant to Section 275(1), or any person pursuant to Section 275(1A), and in accordance with the conditions specified in Section 275, of the SFA, or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA.

Where the Non-CIS Securities are subscribed or purchased under Section 275 of the SFA by a relevant person which is:

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securities (as defined in Section 239(1) of the SFA) of that corporation or the beneficiaries’ rights and interest (howsoever described) in that trust shall not be transferred within six months after that corporation or that trust has acquired the Non-CIS Securities pursuant to an offer made under Section 275 of the SFA except:

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LEGAL MATTERS

The validity of the issuance of the common stock covered by this prospectus supplement will be passed upon for us by Latham & Watkins LLP, Houston, Texas. Certain legal matters in connection with this offering will be passed upon for the underwriters by Vinson & Elkins L.L.P., Houston, Texas.

EXPERTS

The consolidated financial statements and management’s assessment of the effectiveness of internal control over financial reporting (which is included in Management’s Report on Internal Control Over Financial Reporting) incorporated in this Prospectus Supplement by reference to the Annual Report on Form 10-K for the year ended December 31, 2015 have been so incorporated in reliance on the reports of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

Certain information with respect to the oil and gas reserves associated with our oil and gas prospects is derived from the reports of Netherland, Sewell & Associates, Inc., an independent petroleum consulting firm, and has been included in this prospectus supplement, and incorporated by reference herein, upon the authority of said firm as experts with respect to the matters covered by such reports and in giving such reports.

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PROSPECTUS

Southwestern Energy Company

Common Stock

Preferred Stock

Debt Securities

Depositary Shares

Warrants

Purchase Contracts

Units

We may offer and sell the securities identified above from time to time in one or more offerings. This prospectus provides you with a general description of the securities.

Each time we offer and sell securities, we will provide a supplement to this prospectus that contains specific information about the offering and the amounts, prices and terms of the securities. The supplement may also add, update or change information contained in this prospectus with respect to that offering. You should carefully read this prospectus and the applicable prospectus supplement before you invest in any of our securities.

We may offer and sell the securities described in this prospectus and any prospectus supplement to or through one or more underwriters, dealers and agents, or directly to purchasers, or through a combination of these methods. If any underwriters, dealers or agents are involved in the sale of any of the securities, their names and any applicable purchase price, fee, commission or discount arrangement between or among them will be set forth, or will be calculable from the information set forth, in the applicable prospectus supplement. See the sections of this prospectus entitled “About this Prospectus” and “Plan of Distribution” for more information. No securities may be sold without delivery of this prospectus and the applicable prospectus supplement describing the method and terms of the offering of such securities.

INVESTING IN OUR SECURITIES INVOLVES RISKS. SEE THE “RISK FACTORS” ON PAGE 5 OF THIS PROSPECTUS AND ANY SIMILAR SECTION CONTAINED IN THE APPLICABLE PROSPECTUS SUPPLEMENT CONCERNING FACTORS YOU SHOULD CONSIDER BEFORE INVESTING IN OUR SECURITIES.

Our common stock is listed on the New York Stock Exchange under the symbol “SWN.” On November 12, 2015, the last reported sale price of our common stock on the New York Stock Exchange was $10.30 per share.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is November 17, 2015.

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ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the U.S. Securities and Exchange Commission, or the SEC, as a “well-known seasoned issuer” as defined in Rule 405 under the Securities Act of 1933, as amended, using a “shelf” registration process. By using a shelf registration statement, we may sell securities from time to time and in one or more offerings as described in this prospectus. Each time that we offer and sell securities, we will provide a prospectus supplement to this prospectus that contains specific information about the securities being offered and sold and the specific terms of that offering. The prospectus supplement may also add, update or change information contained in this prospectus with respect to that offering. If there is any inconsistency between the information in this prospectus and the applicable prospectus supplement, you should rely on the prospectus supplement. Before purchasing any securities, you should carefully read both this prospectus and the applicable prospectus supplement, together with the additional information described under the heading “Where You Can Find More Information; Incorporation by Reference.”

We have not authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. We will not make an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus and the applicable prospectus supplement to this prospectus is accurate as of the date on its respective cover, and that any information incorporated by reference is accurate only as of the date of the document incorporated by reference, unless we indicate otherwise. Our business, financial condition, results of operations and prospects may have changed since those dates.

When we refer to “Southwestern,” “we,” “our,” “us” and the “Company” in this prospectus, we mean Southwestern Energy Company and its consolidated subsidiaries, unless otherwise specified. When we refer to “you,” we mean the holders of the applicable series of securities.

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WHERE YOU CAN FIND MORE INFORMATION; INCORPORATION BY REFERENCE

Available Information

We file reports, proxy statements and other information with the SEC. Information filed with the SEC by us can be inspected and copied at the Public Reference Room maintained by the SEC at 100 F Street, N.E., Washington, D.C. 20549. You may also obtain copies of this information by mail from the Public Reference Room of the SEC at prescribed rates. Further information on the operation of the SEC’s Public Reference Room in Washington, D.C. can be obtained by calling the SEC at 1-800-SEC-0330. The SEC also maintains a web site that contains reports, proxy and information statements and other information about issuers, such as us, who file electronically with the SEC. The address of that web site is http://www.sec.gov.

Our web site address is www.swn.com. The information on our web site, however, is not, and should not be deemed to be, a part of this prospectus.

This prospectus and any prospectus supplement are part of a registration statement that we filed with the SEC and do not contain all of the information in the registration statement. The full registration statement may be obtained from the SEC or us, as provided below. Forms of the indenture and other documents establishing the terms of the offered securities are or may be filed as exhibits to the registration statement. Statements in this prospectus or any prospectus supplement about these documents are summaries and each statement is qualified in all respects by reference to the document to which it refers. You should refer to the actual documents for a more complete description of the relevant matters. You may inspect a copy of the registration statement at the SEC’s Public Reference Room in Washington, D.C. or through the SEC’s website, as provided above.

Incorporation by Reference

The SEC’s rules allow us to “incorporate by reference” information into this prospectus, which means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus, and subsequent information that we file with the SEC will automatically update and supersede that information. Any statement contained in a previously filed document incorporated by reference will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus modifies or replaces that statement.

We incorporate by reference our documents listed below and any future filings made by us with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, which we refer to as the “Exchange Act” in this prospectus, between the date of this prospectus and the termination of the offering of the securities described in this prospectus. We are not, however, incorporating by reference any documents or portions thereof, whether specifically listed below or filed in the future, that are not deemed “filed” with the SEC, including our Compensation Committee report and performance graph or any information furnished pursuant to Items 2.02 or 7.01 of Form 8-K or related exhibits furnished pursuant to Item 9.01 of Form 8-K.

This prospectus and any accompanying prospectus supplement incorporate by reference the documents set forth below that have previously been filed with the SEC:

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All reports and other documents we subsequently file pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act prior to the termination of this offering but excluding any information furnished to, rather than filed with, the SEC, will also be incorporated by reference into this prospectus and deemed to be part of this prospectus from the date of the filing of such reports and documents.

You may request a free copy of any of the documents incorporated by reference in this prospectus (other than exhibits, unless they are specifically incorporated by reference in the documents) by writing or telephoning us at the following address:

Southwestern Energy Company

10000 Energy Drive

Spring, Texas 77389-4954

Attn. Investor Relations

(832) 796-1000

Exhibits to the filings will not be sent, however, unless those exhibits have specifically been incorporated by reference in this prospectus and any accompanying prospectus supplement.

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THE COMPANY

Southwestern is an independent energy company engaged in natural gas and oil exploration, development and production, or E&P. We are also focused on creating and capturing additional value through our natural gas gathering and marketing businesses, which we refer to as Midstream Services. We operate principally in two segments: E&P and Midstream Services.

Our primary business is the exploration for and production of natural gas and oil, with our current operations principally focused within the United States on development of unconventional reservoirs located in Arkansas, Pennsylvania and West Virginia. Our operations in Arkansas are primarily focused on an unconventional natural gas reservoir known as the Fayetteville Shale, and our operations in northeast Pennsylvania are focused on an unconventional natural gas reservoir known as the Marcellus Shale. We also have a significant stake in properties located in West Virginia and adjacent areas in southwest Pennsylvania. These operations, primarily in West Virginia, are focused on the Marcellus, the Utica and the Upper Devonian unconventional natural gas and oil reservoirs. To a lesser extent, we have exploration and production activities ongoing in Colorado, Louisiana and elsewhere in the United States. We also actively seek to find and develop new natural gas and oil plays with significant exploration and exploitation potential, which we refer to as “New Ventures,” and to obtain additional reserves through acquisitions. We also operate drilling rigs in Arkansas, Pennsylvania and West Virginia, and provide oilfield products and services, principally serving our exploration and production operations. Our natural gas gathering and marketing activities primarily support our E&P activities in Arkansas, Pennsylvania, Louisiana, and West Virginia.

We filed our certificate of incorporation with the Secretary of State of Delaware on February 24, 2006.

Our principal executive offices are located at 1000 Energy Drive, Spring, Texas 77389-4954 and our telephone number is (832) 796-1000.

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RISK FACTORS

Investment in any securities offered pursuant to this prospectus and the applicable prospectus supplement involves risks. You should carefully consider the risk factors incorporated by reference to our most recent Annual Report on Form 10-K and any subsequent Quarterly Reports on Form 10-Q or Current Reports on Form 8-K we file after the date of this prospectus, and all other information contained or incorporated by reference into this prospectus, as updated by our subsequent filings under the Exchange Act, and the risk factors and other information contained in the applicable prospectus supplement before acquiring any of such securities. The occurrence of any of these risks might cause you to lose all or part of your investment in the offered securities.

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

Investors are cautioned that certain statements contained in this prospectus are “forward-looking” statements. Forward-looking statements include, without limitation, any statement that may project, indicate or imply future results, events, performance or achievements, and may contain the words “expect,” “intend,” “plan,” “anticipate,” “estimate,” “believe,” “will be,” “will continue,” “will likely result,” and similar expressions, or future conditional verbs such as “may,” “will,” “should,” “would,” and “could.” In addition, any statement concerning future financial performance (including future revenues, earnings or growth rates), ongoing business strategies or prospects, and possible actions taken by us or our subsidiaries, are also forward-looking statements. These forward-looking statements involve external risks and uncertainties, including, but not limited to, those described under the heading “Risk Factors” and in the documents incorporated by reference herein.

Forward-looking statements are based on current expectations and projections about future events and are inherently subject to a variety of risks and uncertainties, many of which are beyond the control of our management team. All forward-looking statements in this prospectus and subsequent written and oral forward-looking statements attributable to us, or to persons acting on our behalf, are expressly qualified in their entirety by the cautionary statements in this paragraph. These risks and uncertainties include, among others:

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Developments in any of these areas could cause our actual results to differ materially from those anticipated or projected. You should not put undue reliance on any forward-looking statements. When considering forward-looking statements, please review the section titled “Risk Factors” in this prospectus and the risk factors described in any applicable prospectus supplement, together with those in our latest Annual Report on Form 10-K, and any updates to those risk factors included in our subsequent Quarterly Reports on Form 10-Q or Current Reports on Form 8-K. Except as required by applicable securities laws, we undertake no obligation to publicly update or revise any forward-looking statement, whether as a result of new information, future events, changes in assumptions or otherwise.

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USE OF PROCEEDS

We intend to use the net proceeds from the sale of the securities as set forth in the applicable prospectus supplement.

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RATIO OF EARNINGS TO FIXED CHARGES AND PREFERRED SHARE DIVIDENDS

The following table sets forth the historical ratios of earnings to fixed charges and preferred share dividends for Southwestern and its consolidated subsidiaries for the periods indicated.

For the purpose of this calculation, “earnings” consists of (loss) income from continuing operations before income taxes, income on equity method investments, fixed charges (excluding interest capitalized and amortization of interest capitalized). “Fixed charges” consists of interest expensed and capitalized, amortization of debt discount and related issuance costs and the component of rental expense believed by management to be representative of the interest factor thereon.

Due to the non-cash full cost-ceiling impairments, our earnings were insufficient to cover our fixed charges for the nine months ended September 30, 2015 and the year ended December 31, 2012 by approximately $4,247 million and $1,197 million, respectively.

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DESCRIPTION OF CAPITAL STOCK

Common Stock

As of the date of this prospectus, we are authorized to issue up to 1,250,000,000 shares of common stock, par value $0.01 per share.

We may issue additional shares of our common stock at times and under circumstances so as to have a dilutive effect on our earnings per share, our net tangible book value per share and on the equity ownership of the holders of our common stock. If we issue shares of our common stock, the prospectus supplement relating to an offering will set forth the information regarding any dilutive effect of that offering.

The following description is a summary of the material provisions of our common stock but does not purport to be complete and is subject to, and qualified in its entirety by reference to, our certificate of incorporation and our bylaws, which are incorporated by reference as exhibits to the registration statement of which this prospectus forms a part. You should refer to our certificate of incorporation and bylaws for additional information.

Listing

Our common stock is listed on the New York Stock Exchange under the symbol “SWN.” Any additional common stock that we issue will also be listed on the New York Stock Exchange, unless otherwise indicated in a prospectus supplement.

Dividends

We do not currently pay cash dividends on our common stock and we do not anticipate paying cash dividends in the foreseeable future. Any future determination to pay cash dividends will be at the discretion of our board of directors and will be dependent upon our financial condition, results of operation, capital requirements and other factors that our board of directors deems to be relevant.

Fully Paid

All of our outstanding shares of common stock are fully paid and non-assessable. Any additional shares of common stock will also be fully paid and non-assessable when issued.

Voting Rights

Holders of our common stock are entitled to one vote per share on all matters voted on by our stockholders, including the election of directors.

Other Provisions

We will notify holders of our common stock of any stockholders’ meetings in accordance with applicable law. If we liquidate, dissolve or wind-up, whether voluntarily or not, our common stockholders will share equally in the assets remaining after we pay our creditors. Our board of directors may make rules and regulations concerning the transfer of shares of our common stock from time to time, in accordance with our bylaws. Holders of our common stock will have no conversion, sinking fund or redemption rights.

Transfer Agent

The transfer agent and registrar of our common stock is Computershare Trust Company N.A.

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Preferred Stock

Our board of directors has the authority, without further action by our stockholders, to issue up to 10,000,000 shares of preferred stock, par value $0.01 per share, in one or more series. Our board of directors may designate the number of shares constituting any series and the rights, preferences, privileges and restrictions of such preferred stock, including dividend rights, conversion rights, voting rights, terms of redemption, liquidation preference and sinking fund terms, but no shares of any series of preferred stock may be issued without the approval of shareholders if (i) the voting rights of the shares of such series would be materially disproportionate to the voting rights of the shares of common stock or (ii) the shares of such series would be convertible into a materially disproportionate number of shares of common stock, in each case taking into account the issue price of the shares of such series and the fair market value of the shares of common stock at the time of such issuance. The issuance of our preferred stock could adversely affect the voting power of holders of common stock and the likelihood that holders of common stock will receive dividend payments and payments upon liquidation.

Undesignated Preferred Stock

This summary of the undesignated preferred stock discusses terms and conditions that may apply to preferred stock offered under this prospectus. The applicable prospectus supplement will describe the particular terms of each series of preferred stock actually offered. If indicated in the prospectus supplement, the terms of any series may differ from the terms described below.

The following description, together with any applicable prospectus supplement, summarizes all the material terms and provisions of any preferred stock being offered by this prospectus. It does not restate the terms and provisions in their entirety. We urge you to read our charter and the applicable certificate of designation (each, as filed with the SEC) because they, and not this description, define the rights of any holders of preferred stock. We have filed our charter as an exhibit to the registration statement which includes this prospectus. We will incorporate by reference as an exhibit to the registration statement the form of any certificate of designation before the issuance of any series of preferred stock.

The prospectus supplement for any preferred stock that we actually offer pursuant to this prospectus may include some or all of the following terms:

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Subject to our certificate of incorporation and to any limitations imposed by any then-outstanding preferred stock, we may issue additional series of preferred stock, at any time or from time to time, with such powers, preferences, rights and qualifications, limitations or restrictions as the board of directors determines, and without further action of the stockholders, including holders of our then outstanding preferred stock, if any.

Anti-Takeover Effects of Provisions of Our Certificate of Incorporation and Bylaws and Delaware Law

The following provisions of our certificate of incorporation and bylaws and the following provisions of Delaware law may have the effect of delaying, deterring or preventing a change of control of us.

Certificate of Incorporation and Bylaws

Our certificate of incorporation and bylaws include provisions:

The Delaware General Corporation Law

We are subject to the provisions of Section 203 of the Delaware General Corporation Law. In general, Section 203 prohibits a publicly held Delaware corporation from engaging in a “business combination” with an “interested stockholder” for a period of three years after the date of the transaction in which the person became an interested stockholder, unless the business combination is approved in a prescribed manner.

Section 203 defines a “business combination” as a merger, asset sale or other transaction resulting in a financial benefit to an interested stockholder. Section 203 defines an “interested stockholder” as a person who, together with affiliates and associates, owns, or, in some cases, within three years prior, did own, 15% or more of the corporation’s voting stock. Under Section 203, a business combination between us and an interested stockholder is prohibited unless:

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This provision has an anti-takeover effect with respect to transactions not approved in advance by our board of directors, including discouraging takeover attempts that might result in a premium over the market price for the shares of our common stock. With approval of our stockholders, we could amend our certificate of incorporation in the future to elect not to be governed by this provision. This election would be effective 12 months after the adoption of the amendment and would not apply to any business combination between us and any person who became an interested stockholder on or before the adoption of the amendment.

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DESCRIPTION OF DEBT SECURITIES

The following description, together with the additional information we include in any applicable prospectus supplement, summarizes certain general terms and provisions of the debt securities that we may offer under this prospectus. When we offer to sell a particular series of debt securities, we will describe the specific terms of the series in a supplement to this prospectus. We will also indicate in the supplement to what extent the general terms and provisions described in this prospectus apply to a particular series of debt securities.

We may issue debt securities either separately, or together with, or upon the conversion or exercise of or in exchange for, other securities described in this prospectus. Debt securities may be our senior, senior subordinated or subordinated obligations and, unless otherwise specified in a supplement to this prospectus, the debt securities will be our direct, unsecured obligations and may be issued in one or more series.

The debt securities will be issued under an indenture between us and U.S. Bank National Association, as trustee. We have summarized select portions of the indenture below. The summary is not complete. The form of the indenture has been filed as an exhibit to the registration statement and you should read the indenture for provisions that may be important to you. Capitalized terms used in the summary and not defined herein have the meanings specified in the indenture.

General

The debt securities that we may offer under the indenture are not limited in aggregate principal amount. We may issue debt securities at one or more times in one or more series. Each series of debt securities may have different terms. The terms of any series of debt securities will be described in, or determined by action taken pursuant to, a resolution of our board of directors or a committee appointed by our board of directors, in an officer’s certificate or in a supplement to the indenture relating to that series.

We are not obligated to issue all debt securities of one series at the same time and, unless otherwise provided in the prospectus supplement, we may reopen a series, without the consent of the holders of the debt securities of that series, for the issuance of additional debt securities of that series. Additional debt securities of a particular series will have the same terms and conditions as outstanding debt securities of such series (except for the issue date, the offering price and certain other terms that may be specified in any prospectus supplement relating to such issuance), and will be consolidated with, and form a single series with, such outstanding debt securities.

The debt securities issued by us will be unsecured obligations and will rank equally with all of our other unsecured senior indebtedness.

The prospectus supplement relating to any series of debt securities that we may offer will state the price or prices at which the debt securities will be offered and will contain the specific terms of that series. These terms may include the following:

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Change of Control Event

Unless specified to the contrary in the prospectus supplement with respect to any series of debt securities, if a change of control event occurs, each holder will have the right, pursuant to the terms set forth in the indenture, to require us to repurchase all or any part (in an amount equal to at least the minimum denomination of such series of Securities as specified in the terms thereof or an integral multiple as specified in excess thereof) of such holder’s debt securities at a purchase price in cash equal to 101% of the principal amount of such debt securities plus accrued and unpaid interest, if any, and premium or liquidated damages, if any, up to but excluding the date of purchase (subject to the right of holders of record on any relevant record date to receive interest due on the related relevant interest payment date).

Within 30 days following a change of control event, if we have not (prior to the change of control event) sent a redemption notice for all such securities in connection with any optional redemption that may be permitted pursuant to the terms of each outstanding series of debt securities, we will mail a notice (the “change of control offer”) to each holder of such debt securities to which this provision applies, with a copy to the trustee, stating among other matters:

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On the change of control payment date, we will, to the extent lawful:

The paying agent will promptly mail to each holder of the debt securities of a particular series properly tendered and not properly withdrawn the change of control payment for such debt securities, and the trustee will promptly authenticate and mail (or cause to be transferred by book entry) to each holder new debt securities equal in principal amount to any unpurchased portion of the debt securities surrendered, if any; provided that each such new debt security will be in a principal amount of at least the minimum denomination of such series of debt securities as specified in the relevant prospectus supplement, and in integral multiples of any specified minimum denomination in excess thereof.

If the change of control payment date is on or after an interest record date and on or before the related interest payment date, any accrued and unpaid interest, and additional interest, if any, will be paid to the person in whose name debt securities are registered at the close of business on such record date, and no further interest will be payable to holders who tender pursuant to the change of control offer.

Unless specified to the contrary in the prospectus supplement with respect to any series of debt securities, the provisions described above will be applicable to any change of control event whether or not any other provisions of the indenture are applicable. Except as described above with respect to a change of control event or as otherwise specified in the prospectus supplement with respect to any series of debt securities, the indenture does not contain provisions that permit the holders to require us to repurchase or redeem our debt securities in the event of a takeover, recapitalization or similar transaction. In addition, we will not be required to make a change of control offer with respect to any series of debt securities upon a change of control event if a third party makes the change of control offer with respect to such series of debt securities in the manner, at the times and otherwise in compliance with the requirements set forth in the indenture applicable to a change of control offer made by us and purchases all debt securities to which such offer applies that are validly tendered and not withdrawn under such change of control offer.

We will comply, to the extent applicable, with the requirements of Rule 14e-1 of the Exchange Act and any other securities laws or regulations in connection with any required repurchase of debt securities as a result of a change of control event. To the extent that the provisions of any securities laws or regulations conflict with provisions of the indenture, or compliance with the change of control event provisions of the indenture would constitute a violation of any such laws or regulations, we will comply with the applicable securities laws and regulations and will not be deemed to have breached our obligations described in the indenture by virtue of our compliance with such securities laws or regulations.

Our ability to repurchase debt securities pursuant to a change of control offer may be limited by a number of factors. The occurrence of certain of the events that constitute a change of control would constitute a default under our senior credit facility. In addition, certain events that may constitute a change of control under our senior credit facility and cause a default under that agreement will not constitute a change of control or a change of control event under the indenture. Our future indebtedness or that of our subsidiaries may also contain prohibitions of certain events that would constitute a change of control or require such indebtedness to be

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repurchased upon a change of control or a change of control event. Moreover, the exercise by the holders of their right to require us to repurchase debt securities following a change of control in connection with a change in control event could cause a default under such indebtedness, even if the change of control itself does not, due to the financial effect of such repurchase on us. Finally, our ability to pay cash to the holders upon a repurchase may be limited by our then existing financial resources. There can be no assurance that sufficient funds will be available when necessary to make any required repurchases. Even if sufficient funds were otherwise available, the terms of our senior credit facility and other and/or future indebtedness may, prohibit our prepayment or repurchase of debt securities before their scheduled maturity. Consequently, if we are not able to prepay any such other indebtedness containing similar restrictions or obtain requisite consents, we will be unable to fulfill any repurchase obligations we may have if holders of debt securities exercise their repurchase rights following a change of control, which would result in a default under the indenture. A default under the indenture may result in a cross-default under our senior credit facility. The provisions described above may deter certain mergers, tender offers and other takeover attempts involving us.

We have no present intention to engage in a transaction involving a change of control, although it is possible that we could decide to do so in the future. Subject to the limitations discussed below, we could, in the future, enter into certain transactions, including acquisitions, refinancings or other recapitalizations, that would not constitute a change of control or a change of control event under the indenture, but that could increase the amount of indebtedness outstanding at such time or otherwise affect our capital structure or credit ratings. Restrictions on our ability to incur additional indebtedness are contained in the covenants described under “Covenants—Limitation on Liens” and “Covenants—Limitation on Sale and Leaseback Transactions.” Such restrictions in the indenture can be waived only with the consent of the holders of a majority in principal amount of the debt securities of a particular series then outstanding with respect to such series of debt securities. Except for the limitations contained in such covenants, however, the indenture will not contain any covenants or provisions that may afford holders of the debt securities protection in the event of a highly leveraged transaction.

The definition of “change of control” includes a disposition of all or substantially all of the assets of Southwestern Energy Company (determined on a consolidated basis). Although there is a limited body of case law interpreting the phrase “substantially all,” there is no precise established definition of the phrase under applicable law. Accordingly, in certain circumstances there may be a degree of uncertainty as to whether a particular transaction would involve a disposition of “all or substantially all” of the property or assets of a person. As a result, it may be unclear as to whether a change of control has occurred and whether a holder of debt securities may require us to make an offer to repurchase such debt securities as described above.

The provisions under the indenture relative to our obligation to make an offer to repurchase debt securities as a result of a change of control event may be waived or modified or terminated with respect to each series of debt securities with the written consent of the holders of a majority in principal amount of the debt securities of such series then outstanding (including consents obtained in connection with a tender offer or exchange offer for such debt securities ) prior to the occurrence of such change of control event.

Under the indenture:

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Covenants

Except as described below or in the prospectus supplement with respect to any series of debt securities, we are not restricted by the indenture from incurring, assuming or becoming liable for any type of debt or other obligations, from paying dividends or making distributions on our capital stock or purchasing or redeeming our capital stock. The indenture does not require the maintenance of any financial ratios or specified levels of net worth or liquidity. In addition, with certain exceptions, the indenture does not contain any covenants or other provisions that would limit our right to incur additional indebtedness. The indenture does not contain any provisions that would require us to repurchase or redeem or otherwise modify the terms of any of the debt securities upon a change in control or other events that may adversely affect the creditworthiness of the debt securities, for example, a highly leveraged transaction.

Unless otherwise indicated in the prospectus supplement, covenants contained in the indenture, which are summarized below, will apply to the series of debt securities to which the prospectus supplement relates so long as any of the debt securities of that series are outstanding.

Limitation on Liens. We will not, and will not permit any of our subsidiaries to, incur, assume or guarantee any indebtedness for borrowed money secured by a lien on any (a) productive property, (b) any principal transmission facility or (c) any shares of stock of any subsidiary (collectively, (a), (b) and (c), “principal property”), if the sum, without duplication, of:

exceeds 15% of our consolidated assets, unless we provide that the debt securities will be secured equally and ratably with (or, at our option, prior to) such secured debt.

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The provisions described in the foregoing paragraph do not apply to liens incurred, assumed or guaranteed that do not arise from indebtedness for borrowed money and, without limiting the foregoing, also do not apply to liens on principal property:

In all of the cases set forth above, notwithstanding any stated limitation on the assets that may be subject to such lien, a lien on a specified asset or group or type of assets may include liens on all improvements, additions and accessions thereto and all products and proceeds thereof (including, without limitation, dividends, distributions and increases in respect thereof).

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Under the indenture:

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Limitation on Sale and Leaseback Transactions. Neither we nor any of our subsidiaries may enter into, assume, guarantee or otherwise become liable with respect to any sale and leaseback transaction involving any principal property, unless after giving effect thereto the sum, without duplication, of

does not exceed 15% of our consolidated assets.

This restriction shall not apply to any sale and leaseback transaction if, within 180 days from the effective date of such sale and leaseback transaction, we apply or our subsidiary applies an amount not less than the greater of:

to retire its funded debt, including, for this purpose, any currently maturing portion of such funded debt, or to purchase other property having a fair value at least equal to the fair value of the property leased in such sale and leaseback transaction. This restriction also does not apply to any sale and leaseback transaction (A) between us and any of our subsidiaries or between any of our subsidiaries or (B) for which, at the time the transaction is entered into, the term of the related lease to us or our subsidiary of the property sold pursuant to such transaction is three years or less.

“Funded debt” means all indebtedness for borrowed money owed or guaranteed by us or any of our subsidiaries and any other indebtedness which, under GAAP, would appear as indebtedness on our most recent consolidated balance sheet, which matures by its terms more than 12 months from the date of such consolidated balance sheet or which matures by its terms in less than 12 months but by its terms is renewable or extendible beyond 12 months from the date of such consolidated balance sheet at the option of the borrower.

Consolidation, Merger and Sale of Assets. The indenture provides that we may not consolidate with or merge into any other person or sell, convey or transfer all or substantially all of our assets (determined on a consolidated basis) to any person, unless:

Upon such consolidation, merger, sale, conveyance or transfer, the successor corporation formed by such consolidation or into which we are merged or to which such sale, conveyance or transfer is made will succeed to, and be substituted for, us under the indenture, and the predecessor corporation shall be released from all obligations and covenants under the indenture and the debt securities.

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Events of Default, Notice and Waiver

The indenture provides that if an event of default shall have occurred and be continuing and is known to the trustee with respect to any series of debt securities, then either the trustee or the holders of not less than 25% in outstanding principal amount of the debt securities of that series may declare to be due and payable immediately the outstanding principal amount of the debt securities of the affected series, together with interest, if any, accrued thereon; provided, however, that if the event of default is any of certain events of bankruptcy, insolvency or reorganization, all the debt securities, together with interest, if any, accrued thereon, will become immediately due and payable without further action or notice on the part of the trustee or the holders.

Under the indenture, an event of default with respect to the debt securities of any series is any one of the following events:

The indenture provides that the trustee will, within 90 days after the trustee’s knowledge of a default with respect to the debt securities of any series, give to the holders of debt securities of such series notice of such default known to it, unless cured or waived; provided that except in the case of default in the payment of principal, or interest or premium, if any, on any debt security of such series or in the payment of any sinking fund installment with respect to debt securities of such series, the trustee will be protected in withholding such notice if and so long as the trustee in good faith determines that the withholding of such notice is in the interests of the holders of debt securities of such series. The term “default” for the purpose of this provision means any event that is, or after notice or lapse of time, or both, would become, an event of default.

The indenture contains a provision entitling the trustee, subject to the duty of the trustee during the continuance of an event of default to act with the required standard of care, to be indemnified by the holders before proceeding to exercise any right or power under the indenture at the request of such holders. The indenture provides that the holders of a majority in outstanding principal amount of the debt securities of any series may, subject to certain exceptions, on behalf of the holders of debt securities of such series direct the time, method and place of conducting proceedings for remedies available to the trustee, or exercising any trust or power conferred on the trustee.

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The indenture includes a covenant that we will file annually with the trustee a certificate of no default, or specifying any default that exists.

In certain cases, the holders of a majority in outstanding principal amount of the debt securities of any series may on behalf of the holders of debt securities of such series rescind a declaration of acceleration or waive any past default or event of default with respect to the debt securities of that series except a default not theretofore cured in payment of the principal of, or interest or premium, if any, on any debt security of such series or in respect of a provision which under the indenture cannot be modified or amended without the consent of the holder of each such debt security.

No holder of a debt security of any series will have any right to institute any proceeding with respect to the indenture or the debt securities of any series or for any remedy thereunder unless:

However, such limitations do not apply to a suit instituted by a holder of debt securities for enforcement of payment of the principal of, or premium or interest, if any, on such debt securities on or after the respective due dates expressed in such debt securities after any applicable grace periods have expired.

Notwithstanding the foregoing, the sole remedy for an event of default resulting from:

will be liquidated damages, and holders will not have any right under the indenture to accelerate the maturity of the securities of any series as a result of any such breach except as described below. If an event of default relating to any such obligation continues for 90 days after notice thereof is given in accordance with the indenture, we will pay liquidated damages at an annual rate equal to:

On such 365^th day (or earlier, if such event of default is cured or waived prior to such 365^th day), liquidated damages will cease to accrue, and the securities will be subject to acceleration as provided above if the event of default is continuing. Any such liquidated damages shall be paid to holders in the manner and at the times set forth in the indenture.

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Modification and Waiver

The trustee and we may amend or supplement the indenture or the debt securities of any series without the consent of any holder, in order to:

In addition, except as described below, modifications and amendments of the indenture or the debt securities of any series may be made by the trustee and us with the consent of the holders of a majority in outstanding principal amount of the debt securities affected by such modification or amendment. However, no such modification or amendment may, without the consent of each holder affected thereby:

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Defeasance

The indenture provides that we will be discharged from any and all obligations in respect of the debt securities of any series (except for certain obligations to register the transfer or exchange of the debt securities, to replace stolen, lost or mutilated debt securities, to maintain paying agencies and hold monies for payment in trust and to pay the principal of and interest, if any, on such debt securities), upon the irrevocable deposit with the trustee, in trust, of money and/or U.S. government securities, which through the payment of interest and principal thereof in accordance with their terms provides money in an amount sufficient to pay the principal of (and premium, if any) and interest, if any, in respect of the debt securities of such series on the stated maturity date of such principal and any installment of principal, or interest or premium, if any. Also, the establishment of such a trust will be conditioned on the delivery by us to the trustee of an opinion of counsel reasonably satisfactory to the trustee to the effect that, based upon applicable U.S. federal income tax law or a ruling published by the United States Internal Revenue Service, such a defeasance and discharge will not be deemed, or result in, a taxable event with respect to the holders. For the avoidance of doubt, such an opinion would require a change in current U.S. tax law.

We may also omit to comply with the restrictive covenants, if any, of any particular series of debt securities, other than our covenant to pay the amounts due and owing with respect to such series of debt securities. Thereafter, any such omission shall not be an event of default with respect to the debt securities of such series, upon the deposit with the trustee, in trust, of money and/or U.S. government securities which through the payment of interest and principal in respect thereof in accordance with their terms provides money in an amount sufficient to pay any installment of principal of (and premium, if any) and interest, if any, in respect of debt securities of such series on the stated maturity date of such principal or installment of principal, or interest or premium, if any. Our obligations under the indenture and the debt securities of such series other than with respect to such covenants shall remain in full force and effect. Also, the establishment of such a trust will be conditioned on the delivery by us to the trustee of an opinion of counsel to the effect that such a defeasance and discharge will not be deemed, or result in a taxable event with respect to the holders.

In the event we exercise our option to omit compliance with certain covenants as described in the preceding paragraph and the debt securities of such series are declared due and payable because of the occurrence of any event of default, then the amount of monies and U.S. government securities on deposit with the trustee will be sufficient to pay amounts due on the debt securities of such series at the time of the acceleration resulting from such event of default. We shall in any event remain liable for such payments as provided in the debt securities of such series.

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Satisfaction and Discharge

At our option, we may satisfy and discharge the indenture with respect to the debt securities of any series (except for specified obligations of the trustee and ours, including, among others, the obligations to apply money held in trust) when:

Regarding the Trustee

U.S. Bank National Association is the trustee under the indenture. We maintain banking and other commercial relationships with the trustee and its affiliates in the ordinary course of business.

The indenture contains certain limitations on the right of the trustee, should it become a creditor of ours within three months of, or subsequent to, a default by us to make payment in full of principal of, or interest on, any series of debt securities issued pursuant to the indenture when and as the same becomes due and payable, to obtain payment of claims, or to realize for its own account on property received in respect of any such claim as security or otherwise, unless and until such default is cured. However, the trustee’s rights as a creditor of ours will not be limited if the creditor relationship arises from, among other things:

The indenture does not prohibit the trustee from serving as trustee under any other indenture to which we may be a party from time to time or from engaging in other transactions with us. If the trustee acquires any conflicting interest within the meaning of the Trust Indenture Act and any debt securities issued pursuant to any indenture are in default, it must eliminate such conflict or resign.

Conversion or Exchange Rights

The prospectus supplement will describe the terms, if any, on which a series of debt securities may be convertible into or exchangeable for our common stock. These terms will include provisions as to whether conversion or exchange is mandatory, at the option of the holder or at our option. These provisions may allow or require the number of shares of common stock to be received by holders of such series of debt securities to be adjusted.

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DESCRIPTION OF OTHER SECURITIES

We will set forth in the applicable prospectus supplement a description of any depositary shares, warrants, purchase contracts or units issued by us that may be offered and sold pursuant to this prospectus.

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GLOBAL SECURITIES

Book-Entry, Delivery and Form

Unless we indicate differently in a prospectus supplement, the securities initially will be issued in book-entry form and represented by one or more global notes or global securities, or, collectively, global securities. The global securities will be deposited with, or on behalf of, The Depository Trust Company, New York, New York, as depositary, or DTC, and registered in the name of Cede & Co., the nominee of DTC. Unless and until it is exchanged for individual certificates evidencing securities under the limited circumstances described below, a global security may not be transferred except as a whole by the depositary to its nominee or by the nominee to the depositary, or by the depositary or its nominee to a successor depositary or to a nominee of the successor depositary.

DTC has advised us that it is:

DTC holds securities that its participants deposit with DTC. DTC also facilitates the settlement among its participants of securities transactions, such as transfers and pledges, in deposited securities through electronic computerized book-entry changes in participants’ accounts, thereby eliminating the need for physical movement of securities certificates. “Direct participants” in DTC include securities brokers and dealers, including underwriters, banks, trust companies, clearing corporations and other organizations. DTC is a wholly-owned subsidiary of The Depository Trust & Clearing Corporation, or DTCC. DTCC is the holding company for DTC, National Securities Clearing Corporation and Fixed Income Clearing Corporation, all of which are registered clearing agencies. DTCC is owned by the users of its regulated subsidiaries. Access to the DTC system is also available to others, which we sometimes refer to as indirect participants, that clear through or maintain a custodial relationship with a direct participant, either directly or indirectly. The rules applicable to DTC and its participants are on file with the SEC.

Purchases of securities under the DTC system must be made by or through direct participants, which will receive a credit for the securities on DTC’s records. The ownership interest of the actual purchaser of a security, which we sometimes refer to as a beneficial owner, is in turn recorded on the direct and indirect participants’ records. Beneficial owners of securities will not receive written confirmation from DTC of their purchases. However, beneficial owners are expected to receive written confirmations providing details of their transactions, as well as periodic statements of their holdings, from the direct or indirect participants through which they purchased securities. Transfers of ownership interests in global securities are to be accomplished by entries made on the books of participants acting on behalf of beneficial owners. Beneficial owners will not receive certificates representing their ownership interests in the global securities, except under the limited circumstances described below.

To facilitate subsequent transfers, all global securities deposited by direct participants with DTC will be registered in the name of DTC’s partnership nominee, Cede & Co., or such other name as may be requested by an authorized representative of DTC. The deposit of securities with DTC and their registration in the name of Cede & Co. or such other nominee will not change the beneficial ownership of the securities. DTC has no knowledge of the actual beneficial owners of the securities. DTC’s records reflect only the identity of the direct participants to whose accounts the securities are credited, which may or may not be the beneficial owners. The participants are responsible for keeping account of their holdings on behalf of their customers.

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So long as the securities are in book-entry form, you will receive payments and may transfer securities only through the facilities of the depositary and its direct and indirect participants. We will maintain an office or agency in the location specified in the prospectus supplement for the applicable securities, where notices and demands in respect of the securities and the indenture may be delivered to us and where certificated securities may be surrendered for payment, registration of transfer or exchange.

Conveyance of notices and other communications by DTC to direct participants, by direct participants to indirect participants and by direct participants and indirect participants to beneficial owners will be governed by arrangements among them, subject to any legal requirements in effect from time to time.

Redemption notices will be sent to DTC. If less than all of the securities of a particular series are being redeemed, DTC’s practice is to determine by lot the amount of the interest of each direct participant in the securities of such series to be redeemed.

Neither DTC nor Cede & Co. (or such other DTC nominee) will consent or vote with respect to the securities. Under its usual procedures, DTC will mail an omnibus proxy to us as soon as possible after the record date. The omnibus proxy assigns the consenting or voting rights of Cede & Co. to those direct participants to whose accounts the securities of such series are credited on the record date, identified in a listing attached to the omnibus proxy.

So long as securities are in book-entry form, we will make payments on those securities to the depositary or its nominee, as the registered owner of such securities, by wire transfer of immediately available funds. If securities are issued in definitive certificated form under the limited circumstances described below, we will have the option of making payments by check mailed to the addresses of the persons entitled to payment or by wire transfer to bank accounts in the United States designated in writing to the applicable trustee or other designated party at least 15 days before the applicable payment date by the persons entitled to payment, unless a shorter period is satisfactory to the applicable trustee or other designated party.

Redemption proceeds, distributions and dividend payments on the securities will be made to Cede & Co., or such other nominee as may be requested by an authorized representative of DTC. DTC’s practice is to credit direct participants’ accounts upon DTC’s receipt of funds and corresponding detail information from us on the payment date in accordance with their respective holdings shown on DTC records. Payments by participants to beneficial owners will be governed by standing instructions and customary practices, as is the case with securities held for the account of customers in bearer form or registered in “street name.” Those payments will be the responsibility of participants and not of DTC or us, subject to any statutory or regulatory requirements in effect from time to time. Payment of redemption proceeds, distributions and dividend payments to Cede & Co., or such other nominee as may be requested by an authorized representative of DTC, is our responsibility, disbursement of payments to direct participants is the responsibility of DTC, and disbursement of payments to the beneficial owners is the responsibility of direct and indirect participants.

Except under the limited circumstances described below, purchasers of securities will not be entitled to have securities registered in their names and will not receive physical delivery of securities. Accordingly, each beneficial owner must rely on the procedures of DTC and its participants to exercise any rights under the securities and the indenture.

The laws of some jurisdictions may require that some purchasers of securities take physical delivery of securities in definitive form. Those laws may impair the ability to transfer or pledge beneficial interests in securities.

DTC may discontinue providing its services as securities depositary with respect to the securities at any time by giving reasonable notice to us. Under such circumstances, in the event that a successor depositary is not obtained, securities certificates are required to be printed and delivered.

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As noted above, beneficial owners of a particular series of securities generally will not receive certificates representing their ownership interests in those securities. However, if:

we will prepare and deliver certificates for such securities in exchange for beneficial interests in the global securities. Any beneficial interest in a global security that is exchangeable under the circumstances described in the preceding sentence will be exchangeable for securities in definitive certificated form registered in the names that the depositary directs. It is expected that these directions will be based upon directions received by the depositary from its participants with respect to ownership of beneficial interests in the global securities.

We have obtained the information in this section and elsewhere in this prospectus concerning DTC and DTC’s book-entry system from sources that are believed to be reliable, but we take no responsibility for the accuracy of this information.

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PLAN OF DISTRIBUTION

We may sell the offered securities from time to time:

We will identify the specific plan of distribution, including any underwriters, dealers, agents or direct purchasers and their compensation in the applicable prospectus supplement.

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LEGAL MATTERS

Latham & Watkins LLP, Houston, Texas, will pass upon certain legal matters relating to the issuance and sale of the securities offered hereby on behalf of Southwestern Energy Company. Additional legal matters may be passed upon for us or any underwriters, dealers or agents, by counsel that we will name in the applicable prospectus supplement.

EXPERTS

The financial statements and management’s assessment of the effectiveness of internal control over financial reporting (which is included in Management’s Report on Internal Control over Financial Reporting) incorporated in this Prospectus by reference to the Annual Report on Form 10-K for the year ended December 31, 2014 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

The statement of revenues and direct operating expenses of the Acquired West Virginia and Southwest Pennsylvania Properties included in our Current Reports on Form 8-K/A filed on January 7, 2015 and August 25, 2015 have been so incorporated by reference in reliance on the report of PricewaterhouseCoopers LLP, independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

Estimates of our oil and gas reserves and related future net cash flows and the present value thereof were based on a reserve audit prepared by Netherland, Sewell & Associates, Inc., Houston, Texas, an independent petroleum engineering firm. We have included or incorporated those estimates in this prospectus in reliance upon the authority of such firm as an expert in such matters.

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75,000,000 Shares of Common Stock

PROSPECTUS SUPPLEMENT

Book-Running Manager

Credit Suisse

June     , 2016