SWN Southwestern Energy

Free Writing Prospectus

Filed pursuant to Rule 433

Relating to the

Preliminary Prospectus Supplement dated August 18, 2020 to the

Prospectus dated August 18, 2020

Registration No. 333-238633

Southwestern Energy Company

Pricing Term Sheet

August 18, 2020

$350,000,000 8.375% Senior Notes due 2028

The information in this pricing supplement supplements the preliminary prospectus supplement, dated August 18, 2020 (the “Preliminary Prospectus Supplement”), and supersedes the information in the Preliminary Prospectus Supplement to the extent it is inconsistent with the information in the Preliminary Prospectus Supplement. Terms used herein but not defined herein shall have the respective meanings as set forth in the Preliminary Prospectus Supplement.

*Note: A securities rating is not a recommendation to buy, sell, or hold securities and may be subject to revision or withdrawal at any time.

Delivery of the notes is expected to be made against payment therefor on or about August 27, 2020, which is the seventh business day following the date of pricing of the notes (such settlement being referred to as “T+7”). Under Rule 15c6-1 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), trades in the secondary market generally are required to settle in two business days unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade the notes prior to the second trading day preceding the date on which we deliver the notes to the underwriters for the offering will be required, by virtue of the fact that the notes initially will settle in T+7, to specify an alternate settlement cycle at the time of any such trade to prevent failed settlement and should consult their own advisers.

The issuer has filed a registration statement (including a prospectus) with the Securities and Exchange Commission (the “SEC”) for the offering to which this communication relates. Before you invest, you should read the prospectus in that registration statement and other documents the issuer has filed with the SEC for more complete information about the issuer and this offering. You may get these documents for free by visiting EDGAR on the SEC web site at www.sec.gov. Alternatively, any underwriter or any dealer participating in the

offering will arrange to send you the Preliminary Prospectus Supplement and the accompanying prospectus if you request it by calling or emailing Citigroup Global Markets Inc. toll-free at 1-800-831-9146, BofA Securities, Inc. toll-free at 1-800-294-1322 or dg.prospectus_requests@bofa.com or Wells Fargo Securities, LLC at 1-704-410-4874 (with such fax to be confirmed by telephone to 1-704-410-4885) or IBCMDCMLSHYLeveragedSyndicate@wellsfargo.com.

Any disclaimers or notices that may appear on this Pricing Term Sheet below the text of this legend are not applicable to this Pricing Term Sheet and should be disregarded. Such disclaimers may have been electronically generated as a result of this Pricing Term Sheet having been sent via, or posted on, Bloomberg or another electronic mail system.