6-K

FORM 6-K

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

Report of Foreign Private Issuer

Pursuant to Rule 13a - 16 or 15d - 16 of

the Securities Exchange Act of 1934

SUNCOR ENERGY INC.

(Name of registrant)

150 – 6th Avenue S.W.

P.O. Box 2844

Calgary, Alberta

Canada, T2P 3E3

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F:

Form 20-F    ¨                               Form 40-F    x

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

EXHIBIT INDEX

Exhibit 99.1

Suncor Energy announces $1 billionmedium term note offering

All financial figures are in Canadian dollars.

Calgary, Alberta (November 6,2025) – Suncor Energy (TSX: SU) (NYSE: SU) announced today that it has priced an offering of $1 billion in aggregate principal amount of senior unsecured notes. The offering will be comprised of two tranches, consisting of $500 million principal amount of Series 11 Medium Term Notes due on November 14, 2027 having a coupon of 2.95% and $500 million principal amount of Series 12 Medium Term Notes due on November 14, 2030 having a coupon of 3.55%, (together, the “Notes”). The offering is expected to close on November 14, 2025, subject to customary closing conditions.

Suncor intends to use the net proceeds from the sale of the Notes to repay existing debt.

The Notes are being offered through a syndicate of dealers led by TD Securities, CIBC Capital Markets, RBC Capital Markets, and Scotia Capital under Suncor’s short form base shelf prospectus dated June 4, 2024 and related pricing supplements dated November 6, 2025.

This news release does not constitute an offer to sell or the solicitation of an offer to buy any of the Notes in any jurisdiction. The Notes have not been approved or disapproved by any regulatory authority. The Notes have not been and will not be registered under the United States Securities Act of 1933, as amended (the “U.S. Securities Act”), or any state securities laws, and may not be offered or sold within the United States unless an exemption from the registration requirements of the U.S. Securities Act is available.

Legal Advisory – Forward-LookingStatements

This news release contains certainforward-looking information and forward-looking statements (collectively referred to herein as “forward-looking statements”)within the meaning of applicable Canadian and U.S. securities laws. Forward-looking statements in this news release include Suncor’sexpectations regarding the offering of Notes, including the expected closing date of the offering and the intended use of the net proceedstherefrom. Forward-looking statements are not guarantees of future performance and involve a number of risks and uncertainties, somethat are similar to other oil and gas companies and some that are unique to Suncor. Suncor’s actual results may differ materiallyfrom those expressed or implied by its forward-looking statements, so readers are cautioned not to place undue reliance on them.

Suncor’s Management’sDiscussion and Analysis for the third quarter of 2025 dated November 4, 2025, its Annual Information Form, Annual Report to Shareholdersand Form 40-F, each dated February 26, 2025, and other documents it files from time to time with securities regulatory authoritiesdescribe the risks, uncertainties, material assumptions and other factors that could influence actual results and such factors are incorporatedherein by reference. Copies of these documents are available without charge from Suncor at 150 6th Avenue S.W., Calgary, Alberta T2P3E3; by e-mail request to invest@suncor.com; or by referring to suncor.com/FinancialReports or to the company’s profileon SEDAR+ at sedarplus.ca or EDGAR at sec.gov. Except as required by applicable securities laws, Suncor disclaims any intentionor obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.

Suncor Energy is Canada’s leadingintegrated energy company. Suncor’s operations include oil sands development, production and upgrading; offshore oil production;petroleum refining in Canada and the U.S.; and the company’s Petro-Canada^TM^ retail and wholesale distribution networks(including Canada’s Electric Highway^TM^, a coast-to-coast network of fast-charging EV stations). Suncor is developingpetroleum resources while advancing the transition to a lower-emissions future through investments in lower emissions intensity power,renewable feedstock fuels and projects targeting emissions intensity. Suncor also conducts energy trading activities focused primarilyon the marketing and trading of crude oil, natural gas, byproducts, refined products and power. Suncor’s common shares (symbol:SU) are listed on the Toronto and New York stock exchanges.

For more information about Suncor, visit our website at suncor.com.

Media inquiries:

(833) 296-4570

media@suncor.com

Investor inquiries:

invest@suncor.com