CSTM Constellium SE

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 April 2023

Commission File Number: 001-35931

(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  ☒            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): Yes  ☐   No  ☒

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): Yes  ☐   No  ☒

INFORMATION CONTAINED IN THIS FORM 6-K REPORT

Attached hereto as Exhibit 99.1 is a copy of the press release of Constellium SE (the “Company”), dated April 26, 2023, announcing its financial results for the quarter ended March 31, 2023.

Attached hereto as Exhibit 99.2 is a copy of a presentation of the Company, dated April 26, 2023, summarizing its financial results for the quarter ended March 31, 2023.

Exhibit Index

The information contained in Exhibit 99.1 of this Form 6-K (except for the second paragraph containing certain quotes by the Chief Executive Officer, and the section titled “Outlook”), is incorporated by reference into any offering circular or registration statement (or into any prospectus that forms a part thereof) filed by Constellium SE with the Securities and Exchange Commission. Exhibit 99.2 is not incorporated by reference.