6-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of December 2025

Commission File Number: 001-15214

TransAlta Corporation

(Translation of registrant’s name into English)

Suite 1400, 1100—1st Street S.E., Calgary, Alberta, T2G 1B1

(Address of principal executive office)

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 ☒

INCORPORATION BY REFERENCE

Exhibit 99.1 of this Form 6-K is incorporated by reference as an additional exhibit to the registrant’s Registration Statement on Form F-10 (File No. 333-292019).

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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.

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EXHIBIT INDEX

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EX-99.1

Exhibit 99.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the reference to our firm under the caption “Experts” in the Prospectus Supplement, dated December 11, 2025, to the Registration Statement (Form F-10) and related short form base shelf prospectus of TransAlta Corporation (the “Corporation”) for the offering of senior notes and to the inclusion therein of our reports dated February 19, 2025 with respect to the consolidated financial statements of the Corporation as of December 31, 2024 and 2023 and for each of the three years in the period ended December 31, 2024, and with respect to the effectiveness of internal control over financial reporting as of December 31, 2024 included in the Corporation’s Annual Report on Form 40-F filed with the Securities and Exchange Commission.