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Exhibit 21.1
Subsidiaries of Constellium SE as of December 31, 2025

Subsidiary
Jurisdiction
Alcan International Network México S.A. de C.V.
Mexico
AluInfra Services SA
Switzerland
Astrex Inc.
Canada
Constellium Automotive México, S. DE R.L. DE C.V.
Mexico
Constellium Automotive México Trading, S. DE R.L. DE C.V.
Mexico
Constellium Automotive Spain, S.L.
Spain
Constellium Automotive USA, LLC
Delaware
Constellium Automotive Žilina, s.r.o.
Slovak Republic
Constellium Bowling Green LLC
Delaware
Constellium China Co., Ltd.
China
Constellium Deutschland GmbH
Germany
Constellium Engley (Changchun) Automotive Structures Co Ltd.
China
Constellium Extrusions Decin s.r.o.
Czech Republic
Constellium Extrusions France
France
Constellium Extrusions Levice S.r.o.
Slovak Republic
Constellium Finance
France
Constellium France III
France
Constellium France Holdco
France
Constellium Germany Holdco GmbH & Co. KG
Germany
Constellium Germany Verwaltungs GmbH
Germany
Constellium Holdings Muscle Shoals LLC
Delaware
Constellium International
France
Constellium Issoire
France
Constellium Japan KK
Japan
Constellium Metal Procurement LLC
Constellium Montreuil Juigné
Delaware
France
Constellium Muscle Shoals LLC
Delaware
Constellium Muscle Shoals Funding II LLC
Delaware
Constellium Muscle Shoals Funding III LLC
Delaware
Constellium Neuf Brisach
France
Constellium Paris
France
Constellium Rolled Products Ravenswood, LLC
Delaware
Constellium Rolled Products Singen GmbH & Co. KG
Germany
Constellium Singen GmbH
Germany
Constellium Switzerland AG
Switzerland
Constellium Treuhand UG (haftunsgbeschränkt)
Germany
Constellium UK Limited
United Kingdom
Constellium US Holdings I, LLC
Delaware
Constellium US Intermediate Holdings LLC
Delaware
Constellium Valais SA
Switzerland
C-TEC Constellium Technology Center
France
Railtech-Alu-Singen
France