6-K

U.S. 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

Dated February 2, 2024

Commission File Number 1-14878

GERDAU S.A.

(Translation of Registrant’s Name into English)

Av. Dra. Ruth Cardoso, 8,501 – 8° andar

São Paulo, São Paulo - Brazil CEP 05425-070

(Address of principal executive offices)

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

Form 20-F x        Form 40-F ¨

Exhibit Index

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.

Date:  February 2, 2024

Exhibit 99.1

GERDAU S.A.

Corporate Tax ID (CNPJ/MF): 33.611.500/0001-19

Registry (NIRE): 35300520696

MATERIAL FACT

GERDAU S.A. (B3: GGBR / NYSE: GGB) (“Gerdau” or “Company”), in addition to the Material Fact released on January 17, 2024, informs its shareholders and the market in general that, on February 1^st^, 2024, after fulfillment of the corresponding conditions precedent, the divestment of its 50.00% equity interest of the joint venture Gerdau Metaldom Corp. (and subsidiaries) to the INICIA Group has been concluded.

Regarding the divestiture of its 49.85% equity interest of the joint venture Diaco S.A. (and subsidiaries) (“Transaction”), the Company reiterates its estimate that the relevant closing is expected to occur within the first half of 2024, subject to the satisfaction of conditions precedent customary in operations of this nature, particularly the approval by the Colombian antitrust authority.

The Company will keep its shareholders and the market informed about the Transaction’s completion.

São Paulo, February 1^st^, 2024.

Rafael Dorneles Japur

Executive Vice-President and

Investor Relations Officer