GGB 6-K
Gerdau S.A. (GGB)
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
SECURITIESEXCHANGE ACT OF 1934
Dated December 19, 2025
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 of Form 20-F or Form 40-F.
Form 20-F x Form 40-F ¨
Exhibit Index
| Exhibit | Description of Exhibit |
|---|---|
| 99.1 | Material Fact – Buyback program conclusion |
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: December 19, 2025
| GERDAU<br> S.A. | |
|---|---|
| By: | /s/<br> Rafael Dorneles Japur |
| Name: | Rafael<br> Dorneles Japur |
| Title: | Vice-President and Investor Relations Officer |
Exhibit 99.1
GERDAU S.A.
Tax ID (CNPJ) 33.611.500/0001-19
Registry (NIRE): 35300520696
MATERIAL FACT
GERDAU S.A. (B3: GGBR / NYSE: GGB) ("Company") informs its shareholders and the market in general that the share buyback program issued by the Company ("2025 Buyback Program"), disclosed by Material Fact on January 20, 2025, was concluded on this date.
During the period of the buyback, 1,500,000 common shares (GGBR3) were acquired at an average price of R$15.65 per share and 63,000,000 preferred shares (GGBR4 and/or ADRs backed by preferred shares (GGB)) at an average price of R$16.27, corresponding to 100% of the 2025 Buyback Program.
São Paulo, December 19, 2025.
Rafael Dorneles Japur
Executive Vice-President and Investor Relations Officer