6-K

FORM 6-K

U.S. SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

REPORT OF FOREIGN PRIVATE ISSUER

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

SECURITIES EXCHANGE ACT OF 1934

Dated December 16, 2021

Commission File Number 1-14878

GERDAU S.A.

(Exact Name as Specified in its Charter)

       N/A       

(Translation of Registrant’s Name)

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      ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1): ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7): ¨

Indicate by check mark whether by furnishing the information contained in this Form, the registrant is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes    ¨ No    x

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): Not applicable.

SIGNATURES

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

Date:  December 16, 2021

GERDAU S.A.
By:	/s/ Harley Lorentz Scardoelli
Name:  Harley Lorentz Scardoelli
Title:    Investor Relations Director

EXHIBIT INDEX

Exhibit	Description of Exhibit
99.1	Notice to the Market, December 15, 2021

EX-99.1

Exhibit 99.1

GERDAU S.A.

Tax ID (CNPJ/ME): 33.611.500/0001-19

Registry (NIRE): 35300520696

NOTICE TO THE MARKET

Gerdau S.A. (“Company”), in accordance with CVM Resolution 23/2021 (“Resolution”), hereby informs its shareholders and the market that the Board of Directors of the Company approved the engagement of PricewaterhouseCoopers Auditores Independentes (“PwC”) as its independent registered public accounting firm for the fiscal year starting on January 1^st, 2022, in accordance with current legislation.

PwC will replace KPMG Auditores Independentes (“KPMG”) in accordance with in the terms of article 31 of the Resolution, which requires the rotation of the independent auditors and has the consent of KPMG.

The Company also informs that its Board of Auditors (Conselho Fiscal) issued a favorable opinion regarding the engagement of PwC.

São Paulo, December 15^th, 2021.

Harley Lorentz Scardoelli

Executive Vice-President

Investor Relations Officer