13D Filings
Constellium SE
CSTM
Amendment
Ownership

6.20%

Total Shares

8,403,903

Issuer CIK

1563411

Event Date

May 25, 2026

Accepted

May 28, 2026, 04:01 PM

Reporting Persons (4)
Joint Filing

This is a joint filing. The reported shares may overlap between reporting persons and should not be summed.

NameType% of ClassAggregateSole VotingShared Voting
Caisse des Depots (CDC)
Other
6.20%8,403,90308,403,903
Bpifrance Participations S.A.
Other
6.20%8,403,90308,403,903
Bpifrance S.A.
Other
6.20%8,403,90308,403,903
EPIC Bpifrance
Other
6.20%8,403,90308,403,903
Disclosure Items (6)

Security Title

Ordinary Shares, nominal value EUR0.02 per share

Issuer Name

Constellium SE

Issuer Address

300 East Lombard Street, Baltimore, MD, 21202

Principal Occupation

Information concerning the executive officers and directors of Bpifrance Participations, EPIC, Bpifrance, and CDC required to be disclosed in response to Item 2 and General Instruction C to Schedule 13D is provided in Exhibit 99.4 to this Amendment and incorporated herein by reference.

Convictions

None of the Reporting Persons, nor, to the best of their knowledge, any of the persons referred to in Exhibit 99.4 has, during the last five years, been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree, or final order enjoining future violations of, or prohibiting or mandating activities subject to, Federal or state securities laws or finding any violation with respect to such laws.

Item 4 is hereby amended and supplemented as follows: On May 26, 2026, Bpifrance Participations sold 4,190,000 Ordinary Shares by two block trades each at $33.89 per share. All of the Ordinary Shares that are held of record by the Reporting Persons as reported herein were acquired for investment purposes. The Reporting Persons retain the right to change their investment intent, from time to time to acquire additional Ordinary Shares or other securities of the Issuer, or to sell or otherwise dispose of all or part of the Ordinary Shares or other securities of the Issuer, if any, beneficially owned by them, in any manner permitted by law. The Reporting Persons may engage from time to time in ordinary course transactions with financial institutions with respect to the securities described herein. Except as set forth above, none of the Reporting Persons currently has any plans or proposals which would be related to or would result in any of the matters described in Items 4(a)-(j) of the Instructions to Schedule 13D. However, as part of the ongoing evaluation of investment and investment alternatives, the Reporting Persons may consider such matters and, subject to applicable law, may formulate a plan with respect to such matters, and, from time to time, may hold discussions with or make formal proposals to management or the board of directors of the Issuer or other third parties regarding such matters.

Percentage of Class

Item 5(a) of the Schedule 13D is hereby amended and supplemented as follows: As of the date hereof, Bpifrance Participations holds directly 8,403,903 Ordinary Shares, which represents approximately 6.2% of the Issuer's Ordinary Shares. As of the date hereof, none of Bpifrance S.A., CDC, or EPIC holds any Ordinary Shares directly. Bpifrance S.A. may be deemed to be the beneficial owner of 8,403,903 Ordinary Shares, indirectly through its sole ownership of Bpifrance Participations. CDC and EPIC may be deemed to be the beneficial owners of 8,403,903 Ordinary Shares, indirectly through their joint ownership and control of Bpifrance S.A. The ownership percentages are calculated based on 136,150,450 Ordinary Shares outstanding as of April 1, 2026, as reported by the Issuer in its definitive proxy statement filed with the SEC on April 10, 2026.

Number of Shares

Item 5(b) of the Schedule 13D is hereby amended and supplemented as follows: See the information contained on the cover pages of this Amendment, which is incorporated herein by reference.

Transactions

Item 5(c) of the Schedule 13D is hereby amended and supplemented as follows: The information set forth in Item 4 is hereby incorporated by reference to this Item 5(c). Except as disclosed in this Amendment, there have been no reportable transactions with respect to the Ordinary Shares of the Issuer within the last 60 days by the Reporting Persons, or, to the best of their knowledge, any of the persons referred to in Exhibit 99.4.

Item 6 of the Schedule 13D is hereby amended and supplemented as follows: In connection with the block sales described above in Item 4, Bpifrance Participations has agreed, for a period of 60 days, to not offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend or otherwise transfer or dispose of, directly or indirectly, any Ordinary Shares of the Issuer or any securities convertible into or exercisable or exchangeable for Ordinary Shares of the Issuer subject to certain exceptions and approvals.

EX 99.1: Power of Attorney -- CDC (incorporated by reference to Exhibit 1 to Amendment No. 2 to the Schedule 13D filed by Bpifrance Participations on September 7, 2017). EX 99.2: Power of Attorney -- Bpifrance S.A (incorporated by reference to Exhibit 2 to Amendment No. 2 to the Schedule 13D filed by Bpifrance Participations on September 7, 2017). EX 99.3: Power of Attorney -- EPIC and Bpifrance Participations (incorporated by reference to Exhibit 3 to Amendment No. 1 to the Schedule 13G filed by Bpifrance Participations on February 14, 2017). EX 99.4: Information with respect to the Directors and Executive Officers of the Reporting Persons.