Table of Contents Index to Financial Statements UNITED STATES SECURITIES AND EXCHANGE COMMISSION Form 10-K For the fiscal year ended  December 31, 2019 Southwestern Energy Company Washington, D.C. 20549 Commission file number  001-08246 (Exact name of registrant as specified in its charter) Delaware (State or other jurisdiction of incorporation or organization) 71-0205415 (I.R.S. Employer Identification No.) 10000 Energy Drive Spring, Texas 77389 (Address of principal executive offices)(Zip Code) (832) 796-1000 (Registrant’s telephone number, including area code) Securities registered pursuant to Section 12(b) of the Act: Securities registered pursuant to Section 12(g) of the Act:   None Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☒ No ☐ Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes ☐ No ☒ Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐ Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No ☐ Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act. Large accelerated filer ☒ Accelerated filer ☐ Non-accelerated filer ☐ Smaller reporting company ☐ Emerging growth company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐ Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). Yes ☐ No ☒  The aggregate market value of the voting stock held by non-affiliates of the registrant was $1,703,566,444 based on the New York Stock Exchange – Composite Transactions closing price on June 30, 2019 of $3.16. For purposes of this calculation, the registrant has assumed that its directors and executive officers are affiliates. As of February 25, 2020, the number of outstanding shares of the registrant’s Common Stock, par value $0.01, was 541,057,922. Document Incorporated by Reference Portions of the registrant’s definitive proxy statement to be filed with respect to the annual meeting of stockholders to be held on or about May 19, 2020 are incorporated by reference into Part III of this Form 10-K. Title of each class Trading Symbol(s) Name of each exchange on which registered Common Stock, Par Value $0.01 SWN New York Stock Exchange ☒ Annual Report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934