SHARE-BASED COMPENSATION - Schedule of valuation model used for the PSUs granted (Details)	9 Months Ended
	Sep. 30, 2025 $ / shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share price at grant date (in USD per share)	$ 11.90
Performance Shares (PSUs)
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Fair value at grant date (in USD per share)	$ 17.88
Dividend yield	0.00%
Expected volatility	47.00%
Risk-free interest rate (US government bond yield)	3.93%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

CONSTELLIUM SE 10-Q