Constellium SE (CSTM) 6-K 29 Jul 21 Second Quarter Report Financial data

Cover

Cover	6 Months Ended
	Jun. 30, 2021
Cover [Abstract]
Document Type	6-K
Entity Registrant Name	Constellium SE
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001563411
Current Fiscal Year End Date	--12-31

UNAUDITED INTERIM CONSOLIDATED

UNAUDITED INTERIM CONSOLIDATED INCOME STATEMENT - EUR (€) € in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Profit or loss [abstract]
Revenue	€ 1,518	€ 1,031	€ 2,859	€ 2,468
Cost of sales	(1,319)	(957)	(2,518)	(2,241)
Gross profit	199	74	341	227
Selling and administrative expenses	(67)	(57)	(127)	(123)
Research and development expenses	(9)	(7)	(20)	(20)
Other gains and losses - net	44	(11)	87	(79)
Income / (loss) from operations	167	(1)	281	5
Finance costs - net	(37)	(42)	(92)	(87)
Income / (loss) before tax	130	(43)	189	(82)
Income tax (expense) / benefit	(22)	11	(33)	19
Net income / (loss)	108	(32)	156	(63)
Net income attributable to:
Equity holders of Constellium	107	(33)	153	(64)
Non-controlling interests	1	1	3	1
Net income / (loss)	€ 108	€ (32)	€ 156	€ (63)
Earnings per share attributable to the equity holders of Constellium (in Euros)
Basic (in EUR per share)	€ 0.76	€ (0.24)	€ 1.09	€ (0.46)
Diluted (in EUR per share)	€ 0.73	€ (0.24)	€ 1.04	€ (0.46)
Weighted average number of shares
Basic (in shares)	140,636,684	137,901,336	140,301,539	137,903,307
Diluted (in shares)	146,730,106	137,901,336	146,730,106	137,903,307

UNAUDITED INTERIM CONSOLIDATE_2

UNAUDITED INTERIM CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME / (LOSS) - EUR (€) € in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of comprehensive income [abstract]
Net income / (loss)	€ 108	€ (32)	€ 156	€ (63)
Items that will not be reclassified subsequently to the interim income statement
Remeasurement on post-employment benefit obligations	24	(35)	89	(41)
Income tax on remeasurement on post-employment benefit obligations	2	10	(11)	9
Items that may be reclassified subsequently to the interim income statement
Cash flow hedges	3	5	(8)	0
Income tax on hedges	(1)	(2)	2	0
Other comprehensive income / (loss)	(1)	(2)	12	(2)
Other comprehensive income / (loss)	27	(24)	84	(34)
Total comprehensive income / (loss)	135	(56)	240	(97)
Attributable to:
Equity holders of Constellium	134	(57)	236	(98)
Non-controlling interests	1	1	4	1
Total comprehensive income / (loss)	€ 135	€ (56)	€ 240	€ (97)

UNAUDITED INTERIM CONSOLIDATE_3

UNAUDITED INTERIM CONSOLIDATED STATEMENT OF FINANCIAL POSITION - EUR (€)	Jun. 30, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	€ 290,000,000	€ 439,000,000
Trade receivables and other	669,000,000	406,000,000
Inventories	802,000,000	582,000,000
Other financial assets	63,000,000	39,000,000
Total current assets	1,824,000,000	1,466,000,000
Non-current assets
Property, plant and equipment	1,895,000,000	1,906,000,000
Goodwill	430,000,000	417,000,000
Intangible assets	59,000,000	61,000,000
Deferred tax assets	162,000,000	193,000,000
Trade receivables and other	69,000,000	68,000,000
Other financial assets	16,000,000	18,000,000
Total non-current assets	2,631,000,000	2,663,000,000
Total Assets	4,455,000,000	4,129,000,000
Current liabilities
Trade payables and other	1,255,000,000	905,000,000
Borrowings	262,000,000	92,000,000
Other financial liabilities	26,000,000	46,000,000
Income tax payable	23,000,000	20,000,000
Provisions	20,000,000	23,000,000
Total current liabilities	1,586,000,000	1,086,000,000
Non-current liabilities
Trade payables and other	32,000,000	32,000,000
Borrowings	1,995,000,000	2,299,000,000
Other financial liabilities	10,000,000	41,000,000
Pension and other post-employment benefit obligations	581,000,000	664,000,000
Provisions	95,000,000	98,000,000
Deferred tax liabilities	12,000,000	10,000,000
Total non-current liabilities	2,725,000,000	3,144,000,000
Total Liabilities	4,311,000,000	4,230,000,000
Equity
Share capital	2,833,547.32	3,000,000
Share premium	420,000,000	420,000,000
Retained deficit and other reserves	(295,000,000)	(538,000,000)
Equity attributable to equity holders of Constellium	128,000,000	(115,000,000)
Non-controlling interests	16,000,000	14,000,000
Total Equity	144,000,000	(101,000,000)
Total Equity and Liabilities	€ 4,455,000,000	€ 4,129,000,000

UNAUDITED INTERIM CONSOLIDATE_4

UNAUDITED INTERIM CONSOLIDATED STATEMENT OF CHANGES IN EQUITY - EUR (€) € in Millions	Total	Share capital	Share premium	Re- measurement	Cash flow hedges	Foreign currency translation reserve	Other reserves	Retained losses	Total	Non-controlling interests
Beginning balance at Dec. 31, 2019	€ (85)	€ 3	€ 420	€ (177)	€ (10)	€ 4	€ 53	€ (389)	€ (96)	€ 11
Net income	(63)							(64)	(64)	1
Other comprehensive loss	(34)			(32)	0	(2)			(34)
Total comprehensive income / (loss)	(97)			(32)	0	(2)		(64)	(98)	1
Share-based compensation	8						8		8
Transactions with non-controlling interests	0									0
Ending balance at Jun. 30, 2020	(174)	3	420	(209)	(10)	2	61	(453)	(186)	12
Beginning balance at Dec. 31, 2019	(85)	3	420	(177)	(10)	4	53	(389)	(96)	11
Net income	(17)							(21)	(21)	4
Other comprehensive loss	(14)			(15)	19	(17)			(13)	(1)
Total comprehensive income / (loss)	(31)			(15)	19	(17)		(21)	(34)	3
Share-based compensation	15						15		15
Transactions with non-controlling interests	0									0
Ending balance at Dec. 31, 2020	(101)	3	420	(192)	9	(13)	68	(410)	(115)	14
Net income	156							153	153	3
Other comprehensive loss	84			78	(6)	11			83	1
Total comprehensive income / (loss)	240			78	(6)	11		153	236	4
Share-based compensation	7						7		7
Transactions with non-controlling interests	(2)									(2)
Ending balance at Jun. 30, 2021	€ 144	€ 3	€ 420	€ (114)	€ 3	€ (2)	€ 75	€ (257)	€ 128	€ 16

UNAUDITED INTERIM CONSOLIDATE_5

UNAUDITED INTERIM CONSOLIDATED STATEMENT OF CASH FLOWS - EUR (€) € in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Statement of cash flows [abstract]
Net income / (loss)	€ 156	€ (63)
Adjustments
Depreciation and amortization	128	132
Impairment of assets	0	5
Pension and other post-employment benefits service costs	17	17
Finance costs - net	92	87
Income tax expense / (benefit)	33	(19)
Unrealized (gains) / losses on derivatives - net and from remeasurement of monetary assets and liabilities - net	(45)	11
Other - net	5	13
Change in working capital
Inventories	(212)	35
Trade receivables	(234)	7
Trade payables	300	(18)
Other	0	15
Change in provisions	(4)	5
Pension and other post-employment benefits paid	(21)	(20)
Interest paid	(72)	(73)
Income tax refunded	5	18
Net cash flows from operating activities	148	152
Purchases of property, plant and equipment	(74)	(100)
Property, plant and equipment grants received	7	2
Proceeds from disposals, net of cash	0	1
Net cash flows used in investing activities	(67)	(97)
Proceeds from issuance of Senior Notes	712	290
Repayments of Senior Notes	(863)	(200)
Repayment of U.S. revolving credit facilities	0	(129)
Proceeds from other borrowings	2	207
Repayments of other borrowings	(9)	(4)
Lease repayments	(17)	(17)
Payment of financing costs and redemption fees	(26)	(9)
Transactions with non-controlling interests	(2)	0
Other financing activities	(29)	2
Net cash flows (used in) / from financing activities	(232)	140
Net (decrease) / increase in cash and cash equivalents	(151)	195
Cash and cash equivalents - beginning of period	439	184
Effect of exchange rate changes on cash and cash equivalents	2	(1)
Cash and cash equivalents - end of period	€ 290	€ 378

GENERAL INFORMATION

GENERAL INFORMATION	6 Months Ended
	Jun. 30, 2021
Disclosure of general information [abstract]
GENERAL INFORMATION	NOTE 1 - GENERAL INFORMATION Constellium is a global leader in the design and manufacture of a broad range of innovative specialty rolled and extruded aluminium products, serving primarily the packaging, aerospace and automotive end-markets. The Group has a strategic footprint of manufacturing facilities located in North America, Europe and China and operates 29 production facilities, 3 R&D centers and 3 administrative centers. The Group has approximately 12,000 employees. Constellium SE, a French Societas Europaea (SE), is the parent company of the Group. The business address (head office) of Constellium SE is located at Washington Plaza, 40-44 rue Washington, 75008 Paris, France. Unless the context indicates otherwise, when we refer to “we”, “our”, “us”, “Constellium”, the “Group” and the “Company” in this document, we are referring to Constellium SE and its subsidiaries.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
	Jun. 30, 2021
Disclosure of summary of significant accounting policies [abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	NOTE 2 - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES 2.1 Basis of preparation The Unaudited Interim Condensed Consolidated Financial Statements (the "Interim Financial Statements") have been prepared in accordance with IAS 34 - Interim Financial Reporting . Accordingly, they do not include all the information and disclosures required in consolidated financial statements and should be read in conjunction with the Group’s Consolidated Financial Statements for the year ended December 31, 2020. In accordance with IAS 1- Presentation of Financial Statements , the Interim Financial Statements are prepared on the assumption that Constellium is a going concern and will continue in operation for the foreseeable future. The accounting policies adopted in the preparation of the Interim Financial Statements are consistent with those followed in the preparation of the Group’s Consolidated Financial Statements for the year ended December 31, 2020, except for the application of the effective tax rate method in accordance with IAS 34 - Interim Financial Reporting . The Interim Financial Statements are presented in millions of Euros, except Earnings per share in Euros. Certain reclassifications may have been made to prior year amounts to conform to the current year presentation. The Interim Financial Statements were authorized for issue by management on July 26, 2021 . 2.2 New and amended standards and interpretations Several amendments apply for the first time in 2021, but have no impact on the Interim Financial Statements of the Group. The Group has not early adopted any other standard, interpretation or amendment that has been issued but is not yet effective. The Group plans to adopt the new standards and interpretations on their required effective dates. 2.3 Judgments in applying accounting policies and key sources of estimation uncertainty The preparation of financial statements requires management to make judgements, estimates and assumptions that affect the reported amounts of revenues, expenses, assets and liabilities, and the accompanying disclosures, and the disclosure of contingent liabilities. These judgments, estimates and assumptions are based on management’s best knowledge of the relevant facts and circumstances, giving consideration to previous experience. However, actual results may differ from the amounts included in the financial statements. In preparing these Interim Financial Statements, the significant judgments made by management in applying the Group’s accounting policies and the key sources of estimation uncertainty were the same as those applied to the Consolidated Financial Statements at and for the year ended December 31, 2020, as well as the application of the effective tax rate method for the determination of the income tax provision. 2.4 Exchange rates The following table summarizes the main exchange rates used for the preparation of the Interim Financial Statements: Average rates Closing rates Foreign exchange rate for 1 Euro Six months ended June 30, At June 30, At December 31, 2021 2020 2021 2020 U.S. Dollars USD 1.2052 1.1018 1.1884 1.2271 Swiss Francs CHF 1.0945 1.0641 1.0980 1.0802 Czech Koruna CZK 25.8508 26.2970 25.4880 26.2420

REVENUE

REVENUE	6 Months Ended
	Jun. 30, 2021
Revenue [abstract]
REVENUE	NOTE 3 - REVENUE Three months ended June 30, Six months ended June 30, (in millions of Euros) 2021 2020 2021 2020 Packaging rolled products 648 456 1,167 980 Automotive rolled products 213 88 421 281 Specialty and other thin-rolled products 43 20 80 52 Aerospace rolled products 100 142 187 365 Transportation, industry, defense and other rolled products 174 105 321 231 Automotive extruded products 176 96 377 295 Other extruded products 164 124 306 264 Total Revenue by product line 1,518 1,031 2,859 2,468 Three months ended June 30, Six months ended June 30, (in millions of Euros) 2021 2020 2021 2020 Germany 373 192 711 479 France 120 67 224 188 United Kingdom 42 39 79 108 Switzerland 17 15 30 27 Other Europe 308 201 587 476 Total Europe 860 514 1,631 1,278 United States 559 413 1,040 974 Asia and Other Pacific 43 61 79 118 All Other 56 43 109 98 Total Revenue by destination of shipment 1,518 1,031 2,859 2,468

OPERATING SEGMENT INFORMATION

OPERATING SEGMENT INFORMATION	6 Months Ended
	Jun. 30, 2021
Disclosure of operating segments [abstract]
OPERATING SEGMENT INFORMATION	NOTE 4 - OPERATING SEGMENT INFORMATION Constellium has three reportable segments - Packaging & Automotive Rolled Products (P&ARP), Aerospace & Transportation (A&T) and Automotive Structures & Industry (AS&I) - and Holdings & Corporate (H&C). 4.1 Segment Revenue Three months ended June 30, Six months ended June 30, 2021 2020 2021 2020 (in millions of Euros) Segment revenue Inter-segment elimination External revenue Segment revenue Inter-segment elimination External revenue Segment revenue Inter-segment elimination External revenue Segment revenue Inter-segment elimination External revenue P&ARP 907 (3) 904 565 (1) 564 1,673 (5) 1,668 1,317 (4) 1,313 A&T 287 (13) 274 250 (3) 247 532 (24) 508 609 (13) 596 AS&I 345 (5) 340 222 (2) 220 695 (12) 683 564 (5) 559 Total 1,539 (21) 1,518 1,037 (6) 1,031 2,900 (41) 2,859 2,490 (22) 2,468 4.2 Segment Adjusted EBITDA and reconciliation of Adjusted EBITDA to Net Income Three months ended June 30, Six months ended June 30, (in millions of Euros) Notes 2021 2020 2021 2020 P&ARP 94 58 162 124 A&T 42 31 61 83 AS&I 41 (1) 79 33 H&C (7) (7) (11) (12) Adjusted EBITDA 170 81 291 228 Metal price lag (A) 54 (25) 85 (40) Start-up and development costs (B) — (2) — (4) Share based compensation costs (3) (5) (7) (8) Losses on pension plan amendments 18 (2) (2) (2) (2) Depreciation and amortization 12, 13 (65) (66) (128) (132) Impairment of assets 12, 13 — (5) — (5) Restructuring costs 5 (2) (11) (3) (11) Unrealized gains / (losses) on derivatives 16 43 44 (10) Unrealized exchange (losses) / gains from the remeasurement of monetary assets and liabilities – net 5 (1) 1 1 (1) Other (C) — (10) — (10) Income / (loss) from operations 167 (1) 281 5 Finance costs - net 7 (37) (42) (92) (87) Income / (loss) before tax 130 (43) 189 (82) Income tax (expense) / benefit 8 (22) 11 (33) 19 Net income / (loss) 108 (32) 156 (63) (A) Metal price lag represents the financial impact of the timing difference between when aluminium prices included within Constellium's Revenue are established and when aluminium purchase prices included in Cost of sales are established. The Group accounts for inventory using a weighted average price basis and this adjustment aims to remove the effect of volatility in LME prices. The calculation of the Group metal price lag adjustment is based on an internal standardized methodology calculated at each of Constellium’s manufacturing sites and is primarily calculated as the average value of product recorded in inventory, which approximates the spot price in the market, less the average value transferred out of inventory, which is the weighted average of the metal element of cost of sales, based on the quantity sold in the period. (B) Start-up and development costs, for the six months ended June 30, 2020 were related to new projects in our AS&I operating segment. (C) Other, in the six months ended June 30, 2020, included €5 million of procurement penalties and termination fees incurred because of the Group's inability to fulfill certain commitments due to the COVID-19 pandemic and a €5 million loss resulting from the discontinuation of hedge accounting for certain forecasted sales that were determined to be no longer expected to occur in light of the COVID-19 pandemic effects. 4.3 Segment capital expenditures Six months ended June 30, (in millions of Euros) 2021 2020 P&ARP (27) (38) A&T (21) (25) AS&I (24) (35) H&C (2) (2) Capital expenditures (74) (100) 4.4 Segment assets (in millions of Euros) At June 30, At December 31, P&ARP 1,983 1,733 A&T 857 765 AS&I 698 668 H&C 386 274 Segment assets 3,924 3,440 Deferred income tax assets 162 193 Cash and cash equivalents 290 439 Other financial assets 79 57 Total Assets 4,455 4,129

OTHER GAINS AND LOSSES_NET

OTHER GAINS AND LOSSES—NET	6 Months Ended
	Jun. 30, 2021
Analysis of income and expense [abstract]
OTHER GAINS AND LOSSES—NET	NOTE 5 - OTHER GAINS AND LOSSES - NET Three months ended June 30, Six months ended June 30, (in millions of Euros) Notes 2021 2020 2021 2020 Realized gains / (losses) on derivatives (A) 31 (32) 45 (44) Losses reclassified from OCI as a result of hedge accounting discontinuation (B) — (5) — (5) Unrealized gains / (losses) on derivatives at fair value through profit and loss - net (A) 17 43 45 (10) Unrealized exchange (losses) / gains from the remeasurement of monetary assets and liabilities – net 4 (1) 1 1 (1) Impairment of assets (C) — (5) — (5) Restructuring costs (D) (2) (11) (3) (11) Losses on pension plan amendments 18 (2) (2) (2) (2) Other 1 — 1 (1) Total other gains and losses - net 44 (11) 87 (79) (A) Realized and unrealized gains and losses are related to derivatives entered into with the purpose of mitigating exposure to volatility in foreign currencies and commodity prices, and that do not qualify for hedge accounting. (B) For the six months ended June 30, 2020, we determined that a portion of the hedged forecasted sales for the second half of 2020 and 2021, to which hedge accounting was applied, were no longer expected to occur. As a result, the fair value of the related derivatives accumulated in equity was reclassified in the Interim Income Statement and resulted in a €5 million loss. (C) In June 2020, the main customer of the Nanjing Automotive Structures plant (China) announced a suspension of its operations and a strategic reorganization. As a result, we tested the asset for impairment and recorded an impairment charge of €5 million for the six months ended June 30, 2020. (D) For the six months ended June 30, 2021 and 2020, restructuring costs amounted to €3 million and €11 million, respectively, and related to headcount reductions in Europe and in the U.S.

CURRENCY GAINS _ (LOSSES)

CURRENCY GAINS / (LOSSES)	6 Months Ended
	Jun. 30, 2021
Analysis of income and expense [abstract]
CURRENCY GAINS / (LOSSES)	NOTE 6 - CURRENCY GAINS / (LOSSES) Three months ended June 30, Six months ended June 30, (in millions of Euros) Notes 2021 2020 2021 2020 Included in Revenue 17 — (2) (1) (5) Included in Cost of sales — 1 — 1 Included in Other gains and losses - net — (5) 8 (6) Total — (6) 7 (10) Realized exchange losses on foreign currency derivatives - net 17 (2) (3) (5) (3) Losses reclassified from OCI as a result of hedge accounting discontinuation 17 — (5) — (5) Unrealized gains / (losses) on foreign currency derivatives - net 17 3 — 11 (2) Exchange (losses) / gains from the remeasurement of monetary assets and liabilities - net (1) 2 1 — Total — (6) 7 (10) See NOTE 16 - Financial Instruments and NOTE 17 - Financial Risk Management for further information regarding the Company’s foreign currency derivatives and hedging activities.

FINANCE COSTS_NET

FINANCE COSTS—NET	6 Months Ended
	Jun. 30, 2021
Analysis of income and expense [abstract]
FINANCE COSTS—NET	NOTE 7 - FINANCE COSTS - NET Three months ended June 30, Six months ended June 30, (in millions of Euros) 2021 2020 2021 2020 Interest expense on borrowings (A) (26) (32) (56) (64) Interest expense on leases (2) (2) (5) (5) Interest cost on pension and other benefits (2) (3) (4) (6) Expenses on factoring arrangements (2) (3) (4) (6) Net loss on settlement of debt (B) (6) — (23) — Realized and unrealized (losses) / gains on debt derivatives at fair value (C) (15) (7) — 1 Realized and unrealized exchange gains / (losses) on financing activities - net (C) 16 8 — (3) Other finance expenses (1) (4) (1) (5) Capitalized borrowing costs (D) 1 1 1 1 Finance expenses (37) (42) (92) (87) Finance costs - net (37) (42) (92) (87) (A) For the six months ended June 30, 2021, interest expense on borrowings included €50 million of interest and €2 million of amortization of arrangement fees related to Constellium SE Senior Notes. For the six months ended June 30, 2020, it included €57 million of interest and €3 million of amortization of arrangement fees related to Constellium SE Senior Notes. (B) On February 24, 2021, Constellium SE tendered and redeemed its $650 million 6.625% Senior Notes due 2025. The net loss on the settlement of debt included redemption fees of €9 million and the write‐off of the outstanding balance of deferred arrangement fees at the date of redemption for €8 million. On June 2, 2021, Constellium SE redeemed its $400 million 5.750% Senior Notes due 2024. The net loss on the settlement of debt included redemption fees of €3 million and the write‐off of the outstanding balance of deferred arrangement fees at the date of redemption for €3 million. (C) The Group hedges the dollar exposure, relating to the principal of its Constellium SE U.S. Dollar Senior Notes, for the portion that has not been used to finance directly or indirectly U.S. Dollar functional currency entities. Changes in the fair value of these hedging derivatives are recognized within Finance costs – net in the Interim Income Statement and largely offset the unrealized results related to Constellium SE U.S. Dollar Senior Notes revaluation. (D) Borrowing costs directly attributable to the construction of assets are capitalized. The capitalization rate was 5% and 6% for the six months ended June 30, 2021 and 2020, respectively.

INCOME TAX

INCOME TAX	6 Months Ended
	Jun. 30, 2021
Income Taxes [Abstract]
INCOME TAX	NOTE 8 - INCOME TAX Income tax expense or benefit is recognized based on the best estimate of the weighted average annual income tax rate expected for the full year. The tax rate applied at June 30, 2021 was impacted by non-recurring transactions and changes in the allocation of income or loss by country.

CASH AND CASH EQUIVALENTS

CASH AND CASH EQUIVALENTS	6 Months Ended
	Jun. 30, 2021
Cash and cash equivalents [abstract]
CASH AND CASH EQUIVALENTS	NOTE 9 - CASH AND CASH EQUIVALENTS Cash in bank and on hand at June 30, 2021 amounted to €290 million and included €25 million held by subsidiaries that operate in countries where capital control restrictions prevent these balances from being immediately available for general use by the other entities within the Group. At December 31, 2020, the amount subject to these restrictions was €26 million.

TRADE RECEIVABLES AND OTHER

TRADE RECEIVABLES AND OTHER	6 Months Ended
	Jun. 30, 2021
Trade and other receivables [abstract]
TRADE RECEIVABLES AND OTHER	NOTE 10 - TRADE RECEIVABLES AND OTHER At June 30, At December 31, (in millions of Euros) Non-current Current Non-current Current Trade receivables - gross — 590 — 345 Impairment — (4) — (4) Total trade receivables - net — 586 — 341 Income tax receivables 39 5 34 15 Other tax receivables — 45 — 33 Contract assets 18 2 23 2 Prepaid expenses 1 21 1 6 Other 11 10 10 9 Total other receivables 69 83 68 65 Total trade receivables and other 69 669 68 406 10.1 Contract assets At June 30, At December 31, (in millions of Euros) Non-current Current Non-current Current Unbilled tooling costs 5 — 9 — Other 13 2 14 2 Total Contract assets 18 2 23 2 10.2 Aging (in millions of Euros) At June 30, At December 31, Not past due 577 333 1 – 30 days past due 8 7 31 – 60 days past due 1 1 61 – 90 days past due — — Greater than 90 days past due — — Total trade receivables - net 586 341 Impairment allowance Revisions to the impairment allowance arising from changes in estimates are included as either additional allowances or recoveries. An allowance was recognized for €0.4 million for the six months ended June 30, 2021 and 2020. None of the amounts included in Other receivables were deemed to be impaired for the six months ended June 30, 2021 and 2020. The maximum exposure to credit risk at the reporting date is the carrying value of each class of receivable shown above. The Group does not hold any collateral from its customers or debtors as security. 10.3 Currency concentration (in millions of Euros) At June 30, At December 31, Euro 277 143 U.S. Dollar 289 181 Swiss franc 7 6 Other currencies 13 11 Total trade receivables - net 586 341 10.4 Factoring arrangements The Group factors trade receivables under committed factoring agreements in the United States, France, Germany, Switzerland and the Czech Republic: • In the United States, Constellium Muscle Shoals LLC is party to a factoring agreement with a maximum capacity of $300 million and a maturity date in September 2021 and Constellium Automotive USA LLC is party to a factoring agreement with a maximum capacity of $25 million and a maturity date in December 2021. • The factoring agreement in place for our entities in France has a maximum capacity of €255 million (including a €20 million recourse line) and a maturity date in December 2023. • Factoring agreements in place for our entities in Germany, Switzerland and the Czech Republic have a combined maximum capacity of €150 million and maturity dates in December 2023. In addition, the Group sells receivables from one of its German customers under an uncommitted factoring facility whereby receivables sold are confirmed by the customer. These factoring agreements contain certain customary affirmative and negative covenants, including some relating to the administration and collection of the assigned receivables, the terms of the invoices and the exchange of information, but do not contain maintenance financial covenants. In addition, the commitment of the factor to buy receivables under the Muscle Shoals factoring agreement is subject to certain credit ratings being maintained. The Group was in compliance with all applicable covenants at and for the six months ended June 30, 2021 and 2020. Under the Group’s factoring agreements, most of the trade receivables are sold without recourse. Where the Group has transferred substantially all the risks and rewards of ownership of the receivables, the receivables are derecognized. Some remaining receivables do not qualify for derecognition , as the Group retains substantially all the associated risks and rewards. At June 30, 2021, the total carrying amount of the original assets factored was €587 million, of which €384 million had been derecognized. At December 31, 2020, the total carrying amount of the original assets factored was €514 million, of which €398 million had been derecognized. Amounts due to the factors in respect of trade receivables sold were €1 million and nil at June 30, 2021 and December 31, 2020, respectively.

INVENTORIES

INVENTORIES	6 Months Ended
	Jun. 30, 2021
Subclassifications of assets, liabilities and equities [abstract]
INVENTORIES	NOTE 11 - INVENTORIES (in millions of Euros) At June 30, At December 31, Finished goods 196 149 Work in progress 428 280 Raw materials 137 118 Stores and supplies 87 80 Inventories write down (46) (45) Total inventories 802 582

PROPERTY, PLANT AND EQUIPMENT

PROPERTY, PLANT AND EQUIPMENT	6 Months Ended
	Jun. 30, 2021
Property, plant and equipment [abstract]
PROPERTY, PLANT AND EQUIPMENT	NOTE 12 - PROPERTY, PLANT AND EQUIPMENT (in millions of Euros) Land and Property Rights Buildings Machinery and Equipment Construction Work in Progress Other Total Net balance at January 1, 2021 20 379 1,361 132 14 1,906 Additions — 4 23 54 1 82 Disposals — — (1) — — (1) Depreciation expense — (14) (104) (1) (4) (123) Transfer and other changes — 1 45 (48) 3 1 Effect of changes in foreign exchange rates 1 5 23 1 — 30 Net balance at June 30, 2021 21 375 1,347 138 14 1,895 Cost 37 573 2,579 147 51 3,387 Less accumulated depreciation and impairment (16) (198) (1,232) (9) (37) (1,492) Net balance at June 30, 2021 21 375 1,347 138 14 1,895 Right-of-use assets Right-of-use assets have been included within the same line item as that in which the corresponding underlying assets would be presented if they were owned. (in millions of Euros) Buildings Machinery and Equipment Other Total Net balance at January 1, 2021 112 72 2 186 Additions 4 3 — 7 Depreciation expense (6) (10) — (16) Transfer and other changes — (1) — (1) Effect of changes in foreign exchange rates 1 1 — 2 Net balance at June 30, 2021 111 65 2 178 Cost 147 138 4 289 Less accumulated depreciation and impairment (36) (73) (2) (111) Net balance at June 30, 2021 111 65 2 178 The total expense relating to short-term leases, low value asset leases and variable lease payments that are still recognized as operating expenses was €5 million and €6 million for the six months ended June 30, 2021 and 2020, respectively.

INTANGIBLE ASSETS AND GOODWILL

INTANGIBLE ASSETS AND GOODWILL	6 Months Ended
	Jun. 30, 2021
Intangible assets and goodwill [abstract]
INTANGIBLE ASSETS AND GOODWILL	NOTE 13 - INTANGIBLE ASSETS AND GOODWILL (in millions of Euros) Technology Computer Software Customer relationships Work in Progress Other Total Intangible Assets Goodwill Net balance at January 1, 2021 18 15 13 13 2 61 417 Additions — — — 2 — 2 — Amortization expense (1) (4) — — — (5) — Transfer — 4 — (4) — — — Effect of changes in foreign exchange rates 1 — — — — 1 13 Net balance at June 30, 2021 18 15 13 11 2 59 430 Cost 82 80 38 12 2 214 430 Less accumulated depreciation and impairment (64) (65) (25) (1) — (155) — Net balance at June 30, 2021 18 15 13 11 2 59 430

TRADE PAYABLES AND OTHER

TRADE PAYABLES AND OTHER	6 Months Ended
	Jun. 30, 2021
Trade and other payables [abstract]
TRADE PAYABLES AND OTHER	NOTE 14 - TRADE PAYABLES AND OTHER At June 30, At December 31, (in millions of Euros) Non-current Current Non-current Current Trade payables — 950 — 626 Fixed assets payables — 31 — 27 Employees' entitlements — 165 — 143 Taxes payable other than income tax — 29 — 15 Contract liabilities and other liabilities to customers 3 62 3 81 Other payables 29 18 29 13 Total other 32 305 32 279 Total Trade payables and other 32 1,255 32 905 Contract liabilities and other liabilities to customers At June 30, At December 31, (in millions of Euros) Non-current Current Non-current Current Deferred tooling revenue 2 — 2 — Advance payment from customers — 1 — 2 Unrecognized variable consideration (A) 1 59 1 72 Other — 2 — 7 Total contract liabilities and other liabilities to customers 3 62 3 81 (A) Unrecognized variable consideration consists of expected volume rebates, discounts, incentives, refunds penalties and price concessions. Revenue of €23 million that related to contract liabilities at December 31, 2020 was recognized in the six months ended June 30, 2021. Revenue of €20 million generated in the six months ended June 30, 2021 was deferred. Revenue of €14 million that related to contract liabilities at January 1, 2020 was recognized in the six months ended June 30, 2020. Revenue of €25 million generated in the six months ended June 30, 2020 was deferred.

BORROWINGS

BORROWINGS	6 Months Ended
	Jun. 30, 2021
Borrowings [abstract]
BORROWINGS	NOTE 15 - BORROWINGS 15.1 Analysis by nature At June 30, At December 31, (in millions of Euros) Nominal Value in Currency Nominal rate Nominal Value in Euros (Arrangement fees) Accrued interests Carrying value Carrying Secured Pan-U.S. ABL $ — Floating — — — — — Secured U.S. DDTL $ — Floating — — — — — Secured PGE French Facility € 180 Floating 180 — — 180 180 Secured German Facility € — 2.000% — — — — — Secured Inventory Facility € — Floating — — — — — Senior Unsecured Notes (D) Issued May 2014 and due 2024 (F) $ 400 5.750% — — — — 325 Issued February 2017 and due 2025 (E) $ 650 6.625% — — — — 534 Issued November 2017 and due 2026 $ 500 5.875% 421 (5) 9 425 411 Issued November 2017 and due 2026 € 400 4.250% 400 (4) 6 402 401 Issued June 2020 and due 2028 $ 325 5.625% 274 (6) 1 269 260 Issued February 2021 and due 2029 (E) $ 500 3.750% 421 (7) 5 419 — Issued June 2021 and due 2029 (F) € 300 3.125% 300 (5) 1 296 — Unsecured Revolving Credit Facility € — Floating — — — — — Unsecured Swiss Facility CHF 17 1.175% 16 — — 16 18 Unsecured German Facility € — 2.120% — — — — — Lease liabilities 186 — 1 187 195 Other loans (H) 62 — 1 63 67 Total Borrowings 2,260 (27) 24 2,257 2,391 Of which non-current 1,995 2,299 Of which current 262 92 (A) On April 27, 2021, the Pan-U.S. ABL facility maturity date was extended to April 2026 and the Delayed-Draw Term Loan (the “U.S. DDTL”) expired. (B) On May 20, 2021, we exercised the option to repay the PGE French Facility in May 2022. (C) On February 16, 2021, the Secured Inventory Facility maturity date was extended to April 2023. (D) The Senior Unsecured Notes have been issued by Constellium SE and are guaranteed by certain subsidiaries. (E) On February 24, 2021, Constellium SE issued $500 million Sustainability-Linked Senior Notes due 2029 and bearing an interest rate of 3.750%. Deferred arrangement fees were €7 million. Constellium has established two sustainability performance targets (greenhouse gas emissions intensity and recycled metal input). If Constellium does not satisfy the first target for the year ended December 31, 2025, the interest rate will be increased by 0.125% starting April 15, 2026. If Constellium does not satisfy the second target for the year ended December 31, 2026, the interest rate will be increased by 0.125%starting April 15, 2027 (in addition to any increase arising from failure to meet the first target). The net proceeds from the issuance were used to retire the $650 million 6.625% Senior Notes due 2025. (F) On June 2, 2021, Constellium SE issued €300 million Sustainability-Linked Senior Notes due 2029 and bearing an interest rate of 3.125%. Deferred arrangement fees were €5 million. Constellium has established two sustainability performance targets (greenhouse gas emissions intensity and recycled metal input). If Constellium does not satisfy the first target for the year ended December 31, 2025, the interest rate will be increased by 0.125%, starting July 15, 2026. If Constellium does not satisfy the second target for the year ended December 31, 2026, the interest rate will be increased by 0.125%, starting July 15, 2027 (in addition to any increase arising from failure to meet the first target). The net proceeds from the issuance were used to retire the $400 million 5.750% Senior Notes due 2024. (G) The Unsecured Revolving Credit Facility of one of our French entities has a €2 million borrowing base and is provided by Bpifrance Financement, a related party. (H) Other loans include €42 million of financial liabilities relating to the sale and leaseback of assets that were considered to be financing arrangements in substance. 15.2 Covenants The Group was in compliance with all applicable debt covenants at June 30, 2021 and December 31, 2020 and for the six months ended June 30, 2021. 15.3 Movements in borrowings (in millions of Euros) At June 30, At December 31, At the beginning of the period (January 1) 2,391 2,361 Cash flows Proceeds from issuance of Senior Notes (A) 712 290 Repayment of Senior Notes (A) (863) (200) Repayment of U.S. revolving credit facilities — (129) Proceeds from other borrowings 2 202 Repayments of other borrowings (9) (10) Lease repayments (17) (35) Payment of deferred financing costs (12) (6) Non-cash changes Movement in interest accrued (8) (1) Changes in leases and other loans 8 62 Deferred arrangement fees 13 5 Effects of changes in foreign exchange rates 40 (148) At the end of the period 2,257 2,391 (A) On February 24, 2021, Constellium SE issued $500 million 3.750% Sustainability-Linked Senior Notes and used the proceeds to tender and redeem the $650 million 6.625% Senior Notes due 2025. On June 2, 2021, Constellium SE issued €300 million 3.125% Sustainability-Linked Senior Notes and used the proceeds to redeem the $400 million 5.750% Senior Notes due 2024. 15.4 Currency concentration (in millions of Euros) At June 30, At December 31, 2020 U.S. Dollar 1,182 1,602 Euro 1,048 757 Other currencies 27 32 Total borrowings 2,257 2,391

FINANCIAL INSTRUMENTS

FINANCIAL INSTRUMENTS	6 Months Ended
	Jun. 30, 2021
Disclosure of detailed information about financial instruments [abstract]
FINANCIAL INSTRUMENTS	NOTE 16 - FINANCIAL INSTRUMENTS 16.1 Financial assets and liabilities by categories At June 30, At December 31, (in millions of Euros) Notes At amortized cost At fair value through profit and loss At fair value through OCI Total At amortized cost At fair value through profit and loss At fair value through OCI Total Cash and cash equivalents 9 290 — — 290 439 — — 439 Trade receivables 10 — — 586 586 — — 341 341 Other financial assets — 73 6 79 3 40 14 57 Total 290 73 592 955 442 40 355 837 At June 30, At December 31, (in millions of Euros) Notes At amortized cost At fair value through profit and loss At fair value through OCI Total At amortized cost At fair value through profit and loss At fair value through OCI Total Trade payables and fixed assets payables 14 981 — — 981 653 — — 653 Borrowings 15 2,257 — — 2,257 2,391 — — 2,391 Other financial liabilities — 34 2 36 — 85 2 87 Total 3,238 34 2 3,274 3,044 85 2 3,131 16.2 Fair values The carrying value of the Group’s borrowings at maturity is the redemption value. The fair values of Constellium SE Senior Notes issued in November 2017, June 2020, February 2021 and June 2021 account for 102%, 108%, 99% and 100%, respectively, of the nominal values and amount to €839 million, €294 million, €418 million and €299 million, respectively, at June 30, 2021. All derivatives are presented at fair value in the Interim Statement of Financial Position. The fair values of the other financial assets and liabilities approximate their carrying values, as a result of their liquidity or short maturity. At June 30, At December 31, (in millions of Euros) Non-current Current Total Non-current Current Total Aluminium and premium future contracts 8 42 50 1 18 19 Energy future contracts — 1 1 — — — Other future contracts 1 3 4 1 1 2 Currency commercial contracts 7 17 24 16 17 33 Margin call — — — — 3 3 Other financial assets - derivatives 16 63 79 18 39 57 Aluminium and premium future contracts 1 7 8 3 6 9 Other future contracts — 1 1 — 1 1 Currency commercial contracts 2 16 18 4 28 32 Currency net debt derivatives (A) 7 2 9 34 11 45 Other financial liabilities - derivatives 10 26 36 41 46 87 (A) For the six months ended June 30, 2021, forward purchases of $325 million versus the Euro using cross currency basis swaps were bought out before their initial maturity in relation with the refinancing of the Senior Notes. This buy-out generated a €27 million cash outflow which is presented in Other financing activities within the Interim Statement of Cash Flow s. 16.3 Valuation hierarchy The following table provides an analysis of financial instruments measured at fair value, grouped into levels based on the degree to which the fair value is observable: • Level 1 is based on a quoted price (unadjusted) in active markets for identical financial instruments. Level 1 includes aluminium, copper and zinc futures that are traded on the LME. • Level 2 is based on inputs other than quoted prices included within Level 1 that are observable for the assets or liabilities, either directly (i.e. prices) or indirectly (i.e. derived from prices). Level 2 includes foreign exchange derivatives. The present value of future cash flows based on the forward or on the spot exchange rates at the balance sheet date is used to value foreign exchange derivatives. • Level 3 is based on inputs for the asset or liability that are not based on observable market data (unobservable inputs). Trade receivables are classified as a Level 3 measurement under the fair value hierarchy. At June 30, At December 31, (in millions of Euros) Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Other financial assets - derivatives 44 35 — 79 20 37 — 57 Other financial liabilities - derivatives 8 28 — 36 9 78 — 87 There was no material transfer of asset and liability categories into or out of Level 1, Level 2 or Level 3 during the six months ended June 30, 2021 or the year ended 2020.

FINANCIAL RISK MANAGEMENT

FINANCIAL RISK MANAGEMENT	6 Months Ended
	Jun. 30, 2021
Disclosure of financial risk management [Abstract]
FINANCIAL RISK MANAGEMENT	NOTE 17 - FINANCIAL RISK MANAGEMENT The Group’s financial risk management strategy focuses on minimizing the cash flow impacts of volatility in foreign currency exchange rates and metal prices, while maintaining the financial flexibility the Group requires in order to successfully execute the Group’s business strategy. Due to Constellium’s capital structure and the nature of its operations, the Group is exposed to the following financial risks: (i) market risk including foreign exchange, commodity price and interest rate risks; (ii) credit risk and (iii) liquidity and capital management risk. The Group's financial institution counterparties may require margin calls should the mark-to-market of our derivatives hedging foreign exchange and commodity price risks exceed a pre-agreed contractual limit. With a view to avoiding possible margin calls for significant market movements, the Group enters into derivatives with a large number of financial counterparties and monitors margin requirements on a daily basis. In addition, the Group (i) ensures that financial counterparts hedging transactional exposure are also hedging foreign currency loan and deposit exposures and (ii) holds a significant liquidity buffer in cash or in availability under its various borrowing facilities 17.1 Market risk i. Commercial transaction exposures The Group has agreed to supply a major customer with fabricated metal products from a Euro functional currency entity and to invoice in U.S. Dollars. The Group entered into significant foreign exchange derivatives that matched related highly probable future conversion sales. The Group designates these derivatives for hedge accounting, with a total nominal amount of $305 million and $330 million at June 30, 2021 and December 31, 2020 respectively, with maturities ranging from 2021 to 2024. The table below details the effect of foreign currency derivatives in the Interim Income Statement and the Interim Statement of Comprehensive Income / (Loss): Three months ended June 30, Six months ended June 30, (in millions of Euros) Notes 2021 2020 2021 2020 Derivatives that do not qualify for hedge accounting Included in Other gains and losses - net Realized (losses) / gains on foreign currency derivatives - net 6 (2) — (4) 2 Unrealized gains / (losses) on foreign currency derivatives - net (A) 6 3 (1) 11 (2) Derivatives that qualify for hedge accounting Included in Other comprehensive income / (loss) Unrealized gains / (losses) on foreign currency derivatives - net 2 2 (9) (6) Gains / (losses) reclassified from cash flow hedge reserve to the Interim Income Statement 1 3 1 6 Included in Revenue (B) Realized (losses) / gains on foreign currency derivatives - net 6 — (3) (1) (5) Unrealized gains on foreign currency derivatives - net 6 — 1 — — Derivatives discontinued from hedge accounting Included in Other gains and losses - net Losses reclassified from OCI as a result of hedge accounting discontinuation (C) 6 — (5) — (5) (A) Gains or losses on the hedging instruments are expected to offset losses or gains on the underlying hedged forecasted sales that will be reflected in the future when these sales are recognized. (B) Derivatives that qualify for hedge accounting are included in Revenue when the related customer invoices have been issued. (C) In the six months ended June 30, 2020, we determined that a portion of the hedged forecasted sales for the second half of 2020 and for 2021, to which hedge accounting was applied, was no longer expected to occur. As a result, the fair value of the related derivatives accumulated in equity was reclassified in the Interim Income Statement and resulted a €5 million loss. ii. Foreign exchange margin calls There were no margin calls at June 30, 2021.The margin requirement related to foreign exchange hedges amounted to €3 million paid as collateral to counterparties at December 31, 2020. iii. Commodities The Group does not apply hedge accounting on commodity derivatives and therefore any mark-to-market movements are recognized in Other gains and losses – net. 17.2 Liquidity and capital risk management The liquidity requirements of the overall Company are funded out of the Company's cash or by drawing on available credit facilities. The internal management of liquidity is optimized by means of cash pooling agreements and/or intercompany loans and deposits between the Company’s operating entities and central Treasury. At June 30, 2021, the borrowing bases for the Pan-U.S. ABL, the French Inventory Facility, and the German Facilities were €337 million, €82 million, and €50 million, respectively. After deduction of amounts drawn and letters of credit, the Group had €461 million outstanding availability under these revolving credit facilities. At June 30, 2021, liquidity was €887 million, comprised of €290 million of cash and cash equivalents and €597 million of available undrawn facilities, including the €461 million described above.

PENSIONS AND OTHER POST-EMPLOYM

PENSIONS AND OTHER POST-EMPLOYMENT BENEFIT OBLIGATIONS	6 Months Ended
	Jun. 30, 2021
Disclosure of employee benefits [Abstract]
PENSION AND OTHER POST-EMPLOYMENT BENEFIT OBLIGATIONS	NOTE 18 - PENSIONS AND OTHER POST-EMPLOYMENT BENEFIT OBLIGATIONS 18.1 Actuarial assumptions Pension and other post-employment benefit obligations were updated based on the discount rates applicable at June 30, 2021. At June 30, At December 31, Discount rate Discount rate Switzerland 0.20% 0.00% U.S. — — Hourly pension 2.75% - 2.95% 2.45% - 2.65% Salaried pension 2.85% 2.55% OPEB 2.85% - 3.15% 2.50% - 2.80% Other benefits 2.50% - 2.90% 2.20% - 2.55% France — — Retirements 0.90% 0.50% Other benefits 0.75% 0.40% Germany 0.95% 0.55% 18.2 Amounts recognized in the Interim Statement of Financial Position At June 30, At December 31, (in millions of Euros) Pension Benefits Other Benefits Total Pension Benefits Other Benefits Total Present value of funded obligation 741 — 741 772 — 772 Fair value of plan assets (504) — (504) (458) — (458) Deficit of funded plans 237 — 237 314 — 314 Present value of unfunded obligation 131 213 344 134 216 350 Net liability arising from defined benefit obligation 368 213 581 448 216 664 18.3 Amounts recognized in the Interim Income Statement Three months ended June 30, 2021 2020 (in millions of Euros) Pension Benefits Other Benefits Total Pension Benefits Other Benefits Total Service cost Current service cost (6) (2) (8) (5) (1) (6) Past service cost — (2) (2) — (2) (2) Net interest (1) (1) (2) (2) (1) (3) Immediate recognition of gains arising over the year — — — — (1) (1) Administration expenses — — — (1) — (1) Total (7) (5) (12) (8) (5) (13) Six months ended June 30, 2021 2020 (in millions of Euros) Pension Benefits Other Benefits Total Pension Benefits Other Benefits Total Service cost Current service cost (11) (4) (15) (11) (3) (14) Past service cost — (2) (2) — (2) (2) Net interest (2) (2) (4) (3) (3) (6) Immediate recognition of gains arising over the year — 1 1 — — — Administration expenses (1) — (1) (1) — (1) Total (14) (7) (21) (15) (8) (23) 18.4 Movement in net defined benefit obligations At June 30, 2021 Defined benefit obligations Plan Assets Net defined benefit liability (in millions of Euros) Pension benefits Other benefits Total At January 1, 2021 906 216 1,122 (458) 664 Included in the Interim Income Statement Current service cost 11 4 15 — 15 Interest cost / (income) 5 2 7 (3) 4 Past service cost — 2 2 — 2 Immediate recognition of gains arising over the year — (1) (1) — (1) Administration expenses — — — 1 1 Included in the Interim Statement of Comprehensive Income / (loss) Remeasurements due to: —actual return less interest on plan assets — — — (43) (43) —changes in financial assumptions (39) (9) (48) — (48) —changes in demographic assumptions — — — — — —experience losses (1) 1 — — — Effects of changes in foreign exchange rates 5 6 11 (3) 8 Included in the Interim Statement of Cash Flows Benefits paid (17) (9) (26) 15 (11) Contributions by the Group — — — (10) (10) Contributions by the plan participants 2 1 3 (3) — At June 30, 2021 872 213 1,085 (504) 581 18.5 Ravenswood OPEB dispute In 2018, the Group announced a plan to transfer certain participants in the Constellium Rolled Products Ravenswood Retiree Medical and Life Insurance Plan (“the Plan”) from a company-sponsored program to a third-party health network that provides similar benefits at a lower cost. This change in benefits resulted in the recognition of a gain of €36 million from negative past service cost, which was reduced by €3 million in 2019, €2 million in 2020 and €2 million in the second quarter of 2021 to reflect delays in the estimated implementation timetable. The United Steelworkers Local Union 5668 (the “Union”) is contesting the OPEB amendments and filed a lawsuit against Constellium Rolled Products Ravenswood, LLC ("Ravenswood") in a federal district court in West Virginia (the “District Court”) seeking to enjoin the Plan changes and to compel arbitration. The District Court issued an order in December 2018, enjoining Ravenswood from implementing the OPEB amendments pending resolution in arbitration. In September 2019, the arbitrator issued a decision ruling against Ravenswood and sustaining the Union’s grievance. Ravenswood filed a motion in the District Court to vacate this decision, which was denied in June 2020. In July 2020, Ravenswood appealed that denial to the Fourth Circuit Court of Appeals and that court decision is still pending. The Group intends to continue to vigorously defend this matter as it believes it has a strong legal position and it is probable that Ravenswood will ultimately prevail and be able to implement the OPEB amendments. 18.6 Net defined benefit obligations by country At June 30, At December 31, (in millions of Euros) Defined benefit obligations Plan assets Net defined benefit liability Defined benefit obligations Plan assets Net defined benefit liability France 163 (5) 158 168 (5) 163 Germany 134 (2) 132 143 (1) 142 Switzerland 295 (248) 47 310 (223) 87 United States 492 (249) 243 500 (229) 271 Other countries 1 — 1 1 — 1 Total 1,085 (504) 581 1,122 (458) 664

PROVISIONS

PROVISIONS	6 Months Ended
	Jun. 30, 2021
Disclosure of other provisions [abstract]
PROVISIONS	NOTE 19 - PROVISIONS (in millions of Euros) Close down and environmental remediation costs Restructuring Legal claims Total At January 1, 2021 88 6 27 121 Allowance — 3 1 4 Amounts used — (3) (2) (5) Unused amounts reversed — (1) (3) (4) Unwinding of discounts (2) — — (2) Effects of changes in foreign exchange rates 1 — — 1 At June 30, 2021 87 5 23 115 Current 7 3 10 20 Non-Current 80 2 13 95 Total Provisions 87 5 23 115 Legal claims and other costs (in millions of Euros) At June 30, At December 31, Litigation 17 21 Disease claims 5 5 Other 1 1 Total Provisions for legal claims and other costs 23 27 Contingencies The Group is involved, and may become involved, in various lawsuits, claims and proceedings relating to customer claims, product liability, employee and retiree benefit matters and other commercial matters. The Group records provisions for pending litigation matters when it determines that it is probable that an outflow of resources will be required to settle the obligation, and such amounts can be reasonably estimated. In some proceedings, the issues raised are or can be highly complex and subject to significant uncertainties and amounts claimed are and can be substantial. As a result, the probability of loss and an estimation of damages are and can be difficult to ascertain. In exceptional cases, when the Group considers that disclosures relating to provisions and contingencies may prejudice its position, disclosures are limited to the general nature of the dispute.

NON-CASH INVESTING AND FINANCIN

NON-CASH INVESTING AND FINANCING TRANSACTIONS	6 Months Ended
	Jun. 30, 2021
Disclosure of cash flow statement [Abstract]
NON-CASH INVESTING AND FINANCING TRANSACTIONS	NOTE 20 - NON-CASH INVESTING AND FINANCING TRANSACTIONS Property, plant and equipment acquired through leases or financed by third parties amounted to €8 million and €25 million for the six months ended June 30, 2021 and 2020, respectively. These leases and financings are excluded from the Interim Statement of Cash Flows as they are non-cash investing transactions. Fair values of vested Restricted Stock Units and Performance Stock Units amounted to €15 million and zero for the six months ended June 30, 2021 and 2020, respectively. They are excluded from the Interim Statement of Cash Flows as non-cash financing activities.

SHARE CAPITAL

SHARE CAPITAL	6 Months Ended
	Jun. 30, 2021
Disclosure of share capital, reserves and other equity interest [Abstract]
SHARE CAPITAL	NOTE 21 - SHARE CAPITAL Share capital amounted to €2,833,547.32 at June 30, 2021, divided into 141,677,366 ordinary shares, each with a nominal value of two cents and fully paid-up. All shares are of the same class and have the right to one vote. (in millions of Euros) Number of shares Share capital Share premium At January 1, 2021 139,962,672 3 420 New shares issued (A) 1,714,694 — — At June 30, 2021 141,677,366 3 420 (A) In the six month ended June 30, 2021, Constellium SE issued and delivered 1,714,694 ordinary shares to certain employees and directors related to share-based compensation plans.

SHARE-BASED COMPENSATION

SHARE-BASED COMPENSATION	6 Months Ended
	Jun. 30, 2021
Share-based payment arrangements [Abstract]
SHARE-BASED COMPENSATION	NOTE 22 - SHARE-BASED COMPENSATION Description of plans Performance-Based Restricted Stock Units (equity-settled) In May 2021, the Company granted Performance Stock Units (PSUs) to selected employees. These units vest after three years from the grant date if the following conditions are met: • A vesting condition under which the beneficiaries must be continuously employed by the Company through the end of the vesting period; and • A performance condition, contingent on the TSR performance of Constellium shares over the vesting period compared to the TSR of specified indices. PSUs will ultimately vest based on a vesting multiplier which ranges from 0% to 200%. The following table lists the inputs to the valuation model used for the PSUs granted in May 2021: May 2021 PSUs Fair value at grant date (in euros) 21.84 Share price at grant date (in euros) 13.90 Dividend yield — Expected volatility (A) 71% Risk-free interest rate (US government bond yield) 0.31% Model used Monte Carlo (A) Volatility in the share prices of the Company and companies included in indices were estimated based on observed historical volatilities over a period equal to the PSU vesting period. The PSUs granted in May 2018 were vested in May 2021 and achieved a TSR performance of 182.9%. 1,161,718 shares related to this vesting were delivered to beneficiaries. Restricted Stock Units Award Agreements (equity-settled) During the six months ended June 30, 2021, the Company granted Restricted Stock Units (RSUs) to a certain number of employees subject to the beneficiaries remaining continuously employed within the Group from the grant date through the end of the vesting period. The vesting period is three years. The fair value of the RSUs awarded is €13.9, being the quoted market price at grant date. Expense recognized during the period In accordance with IFRS 2, share-based compensation is recognized as an expense over the vesting period. The estimate of this expense is based upon the fair value of a potential ordinary share at the grant date. The total expense related to the potential ordinary shares for the six months ended June 30, 2021 and 2020 amounted to €7 million and €8 million, respectively. Movement of potential shares Performance-Based RSU Restricted Stock Units Equity Award Plans Total potential shares At December 31, 2020 2,594,327 2,231,911 32,912 4,859,150 Granted (A) 614,555 534,499 — 1,149,054 Over-performance (B) 526,551 — — 526,551 Vested (1,161,718) (520,064) (32,912) (1,714,694) Forfeited (C) (9,970) (30,815) — (40,785) At June 30, 2021 2,563,745 2,215,531 — 4,779,276 (A) For PSUs, the number of potential shares granted is presented using a vesting multiplier of 100%. (B) When the achievement of TSR performance exceeds the vesting multiplier of 100%, the additional potential shares are presented as over-performance shares. (C) For potential shares related to PSUs, 9,970 were forfeited following the departure of certain beneficiaries and none were forfeited in relation to the non-fulfilment of performance conditions. Antidilutive potential ordinary shares There were 4,880,758 and 4,878,787 potential ordinary shares that could have a dilutive impact but were considered antidilutive due to negative earnings for the three and six months ended June 30, 2020, respectively.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	6 Months Ended
	Jun. 30, 2021
Disclosure of non-adjusting events after reporting period [abstract]
SUBSEQUENT EVENTS	NOTE 23 - SUBSEQUENT EVENTS In July 2021, the two German facilities were not drawn and consequently expired in accordance with their contractual terms.

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
	Jun. 30, 2021
Disclosure of summary of significant accounting policies [abstract]
Basis of preparation	Basis of preparation The Unaudited Interim Condensed Consolidated Financial Statements (the "Interim Financial Statements") have been prepared in accordance with IAS 34 - Interim Financial Reporting . Accordingly, they do not include all the information and disclosures required in consolidated financial statements and should be read in conjunction with the Group’s Consolidated Financial Statements for the year ended December 31, 2020. In accordance with IAS 1- Presentation of Financial Statements , the Interim Financial Statements are prepared on the assumption that Constellium is a going concern and will continue in operation for the foreseeable future. The accounting policies adopted in the preparation of the Interim Financial Statements are consistent with those followed in the preparation of the Group’s Consolidated Financial Statements for the year ended December 31, 2020, except for the application of the effective tax rate method in accordance with IAS 34 - Interim Financial Reporting . The Interim Financial Statements are presented in millions of Euros, except Earnings per share in Euros. Certain reclassifications may have been made to prior year amounts to conform to the current year presentation. The Interim Financial Statements were authorized for issue by management on July 26, 2021 .
New and amended standards and interpretations	New and amended standards and interpretations Several amendments apply for the first time in 2021, but have no impact on the Interim Financial Statements of the Group. The Group has not early adopted any other standard, interpretation or amendment that has been issued but is not yet effective. The Group plans to adopt the new standards and interpretations on their required effective dates.
Judgments in applying accounting policies and key sources of estimation uncertainty	2.3 Judgments in applying accounting policies and key sources of estimation uncertainty The preparation of financial statements requires management to make judgements, estimates and assumptions that affect the reported amounts of revenues, expenses, assets and liabilities, and the accompanying disclosures, and the disclosure of contingent liabilities. These judgments, estimates and assumptions are based on management’s best knowledge of the relevant facts and circumstances, giving consideration to previous experience. However, actual results may differ from the amounts included in the financial statements. In preparing these Interim Financial Statements, the significant judgments made by management in applying the Group’s accounting policies and the key sources of estimation uncertainty were the same as those applied to the Consolidated Financial Statements at and for the year ended December 31, 2020, as well as the application of the effective tax rate method for the determination of the income tax provision.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure of summary of significant accounting policies [abstract]
Schedule of Main Exchange Rates Used for Preparation of Financial Statements	The following table summarizes the main exchange rates used for the preparation of the Interim Financial Statements: Average rates Closing rates Foreign exchange rate for 1 Euro Six months ended June 30, At June 30, At December 31, 2021 2020 2021 2020 U.S. Dollars USD 1.2052 1.1018 1.1884 1.2271 Swiss Francs CHF 1.0945 1.0641 1.0980 1.0802 Czech Koruna CZK 25.8508 26.2970 25.4880 26.2420

REVENUE (Tables)

REVENUE (Tables)	6 Months Ended
	Jun. 30, 2021
Revenue [abstract]
Schedule of Disaggregation Revenue	Three months ended June 30, Six months ended June 30, (in millions of Euros) 2021 2020 2021 2020 Packaging rolled products 648 456 1,167 980 Automotive rolled products 213 88 421 281 Specialty and other thin-rolled products 43 20 80 52 Aerospace rolled products 100 142 187 365 Transportation, industry, defense and other rolled products 174 105 321 231 Automotive extruded products 176 96 377 295 Other extruded products 164 124 306 264 Total Revenue by product line 1,518 1,031 2,859 2,468 Three months ended June 30, Six months ended June 30, (in millions of Euros) 2021 2020 2021 2020 Germany 373 192 711 479 France 120 67 224 188 United Kingdom 42 39 79 108 Switzerland 17 15 30 27 Other Europe 308 201 587 476 Total Europe 860 514 1,631 1,278 United States 559 413 1,040 974 Asia and Other Pacific 43 61 79 118 All Other 56 43 109 98 Total Revenue by destination of shipment 1,518 1,031 2,859 2,468

OPERATING SEGMENT INFORMATION (

OPERATING SEGMENT INFORMATION (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure of operating segments [abstract]
Schedule of Segment Revenue	Three months ended June 30, Six months ended June 30, 2021 2020 2021 2020 (in millions of Euros) Segment revenue Inter-segment elimination External revenue Segment revenue Inter-segment elimination External revenue Segment revenue Inter-segment elimination External revenue Segment revenue Inter-segment elimination External revenue P&ARP 907 (3) 904 565 (1) 564 1,673 (5) 1,668 1,317 (4) 1,313 A&T 287 (13) 274 250 (3) 247 532 (24) 508 609 (13) 596 AS&I 345 (5) 340 222 (2) 220 695 (12) 683 564 (5) 559 Total 1,539 (21) 1,518 1,037 (6) 1,031 2,900 (41) 2,859 2,490 (22) 2,468
Schedule of Segment Adjusted EBITDA and reconciliation of Adjusted EBITDA to Net Income	Three months ended June 30, Six months ended June 30, (in millions of Euros) Notes 2021 2020 2021 2020 P&ARP 94 58 162 124 A&T 42 31 61 83 AS&I 41 (1) 79 33 H&C (7) (7) (11) (12) Adjusted EBITDA 170 81 291 228 Metal price lag (A) 54 (25) 85 (40) Start-up and development costs (B) — (2) — (4) Share based compensation costs (3) (5) (7) (8) Losses on pension plan amendments 18 (2) (2) (2) (2) Depreciation and amortization 12, 13 (65) (66) (128) (132) Impairment of assets 12, 13 — (5) — (5) Restructuring costs 5 (2) (11) (3) (11) Unrealized gains / (losses) on derivatives 16 43 44 (10) Unrealized exchange (losses) / gains from the remeasurement of monetary assets and liabilities – net 5 (1) 1 1 (1) Other (C) — (10) — (10) Income / (loss) from operations 167 (1) 281 5 Finance costs - net 7 (37) (42) (92) (87) Income / (loss) before tax 130 (43) 189 (82) Income tax (expense) / benefit 8 (22) 11 (33) 19 Net income / (loss) 108 (32) 156 (63) (A) Metal price lag represents the financial impact of the timing difference between when aluminium prices included within Constellium's Revenue are established and when aluminium purchase prices included in Cost of sales are established. The Group accounts for inventory using a weighted average price basis and this adjustment aims to remove the effect of volatility in LME prices. The calculation of the Group metal price lag adjustment is based on an internal standardized methodology calculated at each of Constellium’s manufacturing sites and is primarily calculated as the average value of product recorded in inventory, which approximates the spot price in the market, less the average value transferred out of inventory, which is the weighted average of the metal element of cost of sales, based on the quantity sold in the period. (B) Start-up and development costs, for the six months ended June 30, 2020 were related to new projects in our AS&I operating segment. (C) Other, in the six months ended June 30, 2020, included €5 million of procurement penalties and termination fees incurred because of the Group's inability to fulfill certain commitments due to the COVID-19 pandemic and a €5 million loss resulting from the discontinuation of hedge accounting for certain forecasted sales that were determined to be no longer expected to occur in light of the COVID-19 pandemic effects.
Schedule of Segment Capital Expenditures	Six months ended June 30, (in millions of Euros) 2021 2020 P&ARP (27) (38) A&T (21) (25) AS&I (24) (35) H&C (2) (2) Capital expenditures (74) (100)
Schedule of Segment Assets	(in millions of Euros) At June 30, At December 31, P&ARP 1,983 1,733 A&T 857 765 AS&I 698 668 H&C 386 274 Segment assets 3,924 3,440 Deferred income tax assets 162 193 Cash and cash equivalents 290 439 Other financial assets 79 57 Total Assets 4,455 4,129

OTHER GAINS AND LOSSES_NET (Tab

OTHER GAINS AND LOSSES—NET (Tables)	6 Months Ended
	Jun. 30, 2021
Analysis of income and expense [abstract]
Schedule of Other Gains and Losses—Net	Three months ended June 30, Six months ended June 30, (in millions of Euros) Notes 2021 2020 2021 2020 Realized gains / (losses) on derivatives (A) 31 (32) 45 (44) Losses reclassified from OCI as a result of hedge accounting discontinuation (B) — (5) — (5) Unrealized gains / (losses) on derivatives at fair value through profit and loss - net (A) 17 43 45 (10) Unrealized exchange (losses) / gains from the remeasurement of monetary assets and liabilities – net 4 (1) 1 1 (1) Impairment of assets (C) — (5) — (5) Restructuring costs (D) (2) (11) (3) (11) Losses on pension plan amendments 18 (2) (2) (2) (2) Other 1 — 1 (1) Total other gains and losses - net 44 (11) 87 (79) (A) Realized and unrealized gains and losses are related to derivatives entered into with the purpose of mitigating exposure to volatility in foreign currencies and commodity prices, and that do not qualify for hedge accounting. (B) For the six months ended June 30, 2020, we determined that a portion of the hedged forecasted sales for the second half of 2020 and 2021, to which hedge accounting was applied, were no longer expected to occur. As a result, the fair value of the related derivatives accumulated in equity was reclassified in the Interim Income Statement and resulted in a €5 million loss. (C) In June 2020, the main customer of the Nanjing Automotive Structures plant (China) announced a suspension of its operations and a strategic reorganization. As a result, we tested the asset for impairment and recorded an impairment charge of €5 million for the six months ended June 30, 2020. (D) For the six months ended June 30, 2021 and 2020, restructuring costs amounted to €3 million and €11 million, respectively, and related to headcount reductions in Europe and in the U.S.

CURRENCY GAINS _ (LOSSES) (Tabl

CURRENCY GAINS / (LOSSES) (Tables)	6 Months Ended
	Jun. 30, 2021
Analysis of income and expense [abstract]
Schedule of Currency Gains and Losses Included in Income from Operations	Three months ended June 30, Six months ended June 30, (in millions of Euros) Notes 2021 2020 2021 2020 Included in Revenue 17 — (2) (1) (5) Included in Cost of sales — 1 — 1 Included in Other gains and losses - net — (5) 8 (6) Total — (6) 7 (10) Realized exchange losses on foreign currency derivatives - net 17 (2) (3) (5) (3) Losses reclassified from OCI as a result of hedge accounting discontinuation 17 — (5) — (5) Unrealized gains / (losses) on foreign currency derivatives - net 17 3 — 11 (2) Exchange (losses) / gains from the remeasurement of monetary assets and liabilities - net (1) 2 1 — Total — (6) 7 (10)

FINANCE COSTS_NET (Tables)

FINANCE COSTS—NET (Tables)	6 Months Ended
	Jun. 30, 2021
Analysis of income and expense [abstract]
Schedule of Finance Costs—Net	Three months ended June 30, Six months ended June 30, (in millions of Euros) 2021 2020 2021 2020 Interest expense on borrowings (A) (26) (32) (56) (64) Interest expense on leases (2) (2) (5) (5) Interest cost on pension and other benefits (2) (3) (4) (6) Expenses on factoring arrangements (2) (3) (4) (6) Net loss on settlement of debt (B) (6) — (23) — Realized and unrealized (losses) / gains on debt derivatives at fair value (C) (15) (7) — 1 Realized and unrealized exchange gains / (losses) on financing activities - net (C) 16 8 — (3) Other finance expenses (1) (4) (1) (5) Capitalized borrowing costs (D) 1 1 1 1 Finance expenses (37) (42) (92) (87) Finance costs - net (37) (42) (92) (87) (A) For the six months ended June 30, 2021, interest expense on borrowings included €50 million of interest and €2 million of amortization of arrangement fees related to Constellium SE Senior Notes. For the six months ended June 30, 2020, it included €57 million of interest and €3 million of amortization of arrangement fees related to Constellium SE Senior Notes. (B) On February 24, 2021, Constellium SE tendered and redeemed its $650 million 6.625% Senior Notes due 2025. The net loss on the settlement of debt included redemption fees of €9 million and the write‐off of the outstanding balance of deferred arrangement fees at the date of redemption for €8 million. On June 2, 2021, Constellium SE redeemed its $400 million 5.750% Senior Notes due 2024. The net loss on the settlement of debt included redemption fees of €3 million and the write‐off of the outstanding balance of deferred arrangement fees at the date of redemption for €3 million. (C) The Group hedges the dollar exposure, relating to the principal of its Constellium SE U.S. Dollar Senior Notes, for the portion that has not been used to finance directly or indirectly U.S. Dollar functional currency entities. Changes in the fair value of these hedging derivatives are recognized within Finance costs – net in the Interim Income Statement and largely offset the unrealized results related to Constellium SE U.S. Dollar Senior Notes revaluation. (D) Borrowing costs directly attributable to the construction of assets are capitalized. The capitalization rate was 5% and 6% for the six months ended June 30, 2021 and 2020, respectively.

TRADE RECEIVABLES AND OTHER (Ta

TRADE RECEIVABLES AND OTHER (Tables)	6 Months Ended
	Jun. 30, 2021
Trade and other receivables [abstract]
Schedule of Trade Receivables and Other	At June 30, At December 31, (in millions of Euros) Non-current Current Non-current Current Trade receivables - gross — 590 — 345 Impairment — (4) — (4) Total trade receivables - net — 586 — 341 Income tax receivables 39 5 34 15 Other tax receivables — 45 — 33 Contract assets 18 2 23 2 Prepaid expenses 1 21 1 6 Other 11 10 10 9 Total other receivables 69 83 68 65 Total trade receivables and other 69 669 68 406
Schedule of Contract Assets	At June 30, At December 31, (in millions of Euros) Non-current Current Non-current Current Unbilled tooling costs 5 — 9 — Other 13 2 14 2 Total Contract assets 18 2 23 2
Schedule of Aging of Total Trade Receivables—Net	(in millions of Euros) At June 30, At December 31, Not past due 577 333 1 – 30 days past due 8 7 31 – 60 days past due 1 1 61 – 90 days past due — — Greater than 90 days past due — — Total trade receivables - net 586 341
Schedule of Carrying Amounts of Total Trade Receivables—Net by Currency	(in millions of Euros) At June 30, At December 31, Euro 277 143 U.S. Dollar 289 181 Swiss franc 7 6 Other currencies 13 11 Total trade receivables - net 586 341

INVENTORIES (Tables)

INVENTORIES (Tables)	6 Months Ended
	Jun. 30, 2021
Subclassifications of assets, liabilities and equities [abstract]
Schedule of Inventories	(in millions of Euros) At June 30, At December 31, Finished goods 196 149 Work in progress 428 280 Raw materials 137 118 Stores and supplies 87 80 Inventories write down (46) (45) Total inventories 802 582

PROPERTY, PLANT AND EQUIPMENT (

PROPERTY, PLANT AND EQUIPMENT (Tables)	6 Months Ended
	Jun. 30, 2021
Property, plant and equipment [abstract]
Schedule of Property, Plant and Equipment	(in millions of Euros) Land and Property Rights Buildings Machinery and Equipment Construction Work in Progress Other Total Net balance at January 1, 2021 20 379 1,361 132 14 1,906 Additions — 4 23 54 1 82 Disposals — — (1) — — (1) Depreciation expense — (14) (104) (1) (4) (123) Transfer and other changes — 1 45 (48) 3 1 Effect of changes in foreign exchange rates 1 5 23 1 — 30 Net balance at June 30, 2021 21 375 1,347 138 14 1,895 Cost 37 573 2,579 147 51 3,387 Less accumulated depreciation and impairment (16) (198) (1,232) (9) (37) (1,492) Net balance at June 30, 2021 21 375 1,347 138 14 1,895
Schedule of Right of Use Assets	Right-of-use assets have been included within the same line item as that in which the corresponding underlying assets would be presented if they were owned. (in millions of Euros) Buildings Machinery and Equipment Other Total Net balance at January 1, 2021 112 72 2 186 Additions 4 3 — 7 Depreciation expense (6) (10) — (16) Transfer and other changes — (1) — (1) Effect of changes in foreign exchange rates 1 1 — 2 Net balance at June 30, 2021 111 65 2 178 Cost 147 138 4 289 Less accumulated depreciation and impairment (36) (73) (2) (111) Net balance at June 30, 2021 111 65 2 178

INTANGIBLE ASSETS AND GOODWILL

INTANGIBLE ASSETS AND GOODWILL (Tables)	6 Months Ended
	Jun. 30, 2021
Intangible assets and goodwill [abstract]
Schedule of Changes in Intangible Assets and Goodwill	(in millions of Euros) Technology Computer Software Customer relationships Work in Progress Other Total Intangible Assets Goodwill Net balance at January 1, 2021 18 15 13 13 2 61 417 Additions — — — 2 — 2 — Amortization expense (1) (4) — — — (5) — Transfer — 4 — (4) — — — Effect of changes in foreign exchange rates 1 — — — — 1 13 Net balance at June 30, 2021 18 15 13 11 2 59 430 Cost 82 80 38 12 2 214 430 Less accumulated depreciation and impairment (64) (65) (25) (1) — (155) — Net balance at June 30, 2021 18 15 13 11 2 59 430

TRADE PAYABLES AND OTHER (Table

TRADE PAYABLES AND OTHER (Tables)	6 Months Ended
	Jun. 30, 2021
Trade and other payables [abstract]
Schedule of Trade Payables and Other	At June 30, At December 31, (in millions of Euros) Non-current Current Non-current Current Trade payables — 950 — 626 Fixed assets payables — 31 — 27 Employees' entitlements — 165 — 143 Taxes payable other than income tax — 29 — 15 Contract liabilities and other liabilities to customers 3 62 3 81 Other payables 29 18 29 13 Total other 32 305 32 279 Total Trade payables and other 32 1,255 32 905
Schedule of Contract Liabilities	At June 30, At December 31, (in millions of Euros) Non-current Current Non-current Current Deferred tooling revenue 2 — 2 — Advance payment from customers — 1 — 2 Unrecognized variable consideration (A) 1 59 1 72 Other — 2 — 7 Total contract liabilities and other liabilities to customers 3 62 3 81 (A) Unrecognized variable consideration consists of expected volume rebates, discounts, incentives, refunds penalties and price concessions.

BORROWINGS (Tables)

BORROWINGS (Tables)	6 Months Ended
	Jun. 30, 2021
Borrowings [abstract]
Schedule of Borrowings by Nature	At June 30, At December 31, (in millions of Euros) Nominal Value in Currency Nominal rate Nominal Value in Euros (Arrangement fees) Accrued interests Carrying value Carrying Secured Pan-U.S. ABL $ — Floating — — — — — Secured U.S. DDTL $ — Floating — — — — — Secured PGE French Facility € 180 Floating 180 — — 180 180 Secured German Facility € — 2.000% — — — — — Secured Inventory Facility € — Floating — — — — — Senior Unsecured Notes (D) Issued May 2014 and due 2024 (F) $ 400 5.750% — — — — 325 Issued February 2017 and due 2025 (E) $ 650 6.625% — — — — 534 Issued November 2017 and due 2026 $ 500 5.875% 421 (5) 9 425 411 Issued November 2017 and due 2026 € 400 4.250% 400 (4) 6 402 401 Issued June 2020 and due 2028 $ 325 5.625% 274 (6) 1 269 260 Issued February 2021 and due 2029 (E) $ 500 3.750% 421 (7) 5 419 — Issued June 2021 and due 2029 (F) € 300 3.125% 300 (5) 1 296 — Unsecured Revolving Credit Facility € — Floating — — — — — Unsecured Swiss Facility CHF 17 1.175% 16 — — 16 18 Unsecured German Facility € — 2.120% — — — — — Lease liabilities 186 — 1 187 195 Other loans (H) 62 — 1 63 67 Total Borrowings 2,260 (27) 24 2,257 2,391 Of which non-current 1,995 2,299 Of which current 262 92 (A) On April 27, 2021, the Pan-U.S. ABL facility maturity date was extended to April 2026 and the Delayed-Draw Term Loan (the “U.S. DDTL”) expired. (B) On May 20, 2021, we exercised the option to repay the PGE French Facility in May 2022. (C) On February 16, 2021, the Secured Inventory Facility maturity date was extended to April 2023. (D) The Senior Unsecured Notes have been issued by Constellium SE and are guaranteed by certain subsidiaries. (E) On February 24, 2021, Constellium SE issued $500 million Sustainability-Linked Senior Notes due 2029 and bearing an interest rate of 3.750%. Deferred arrangement fees were €7 million. Constellium has established two sustainability performance targets (greenhouse gas emissions intensity and recycled metal input). If Constellium does not satisfy the first target for the year ended December 31, 2025, the interest rate will be increased by 0.125% starting April 15, 2026. If Constellium does not satisfy the second target for the year ended December 31, 2026, the interest rate will be increased by 0.125%starting April 15, 2027 (in addition to any increase arising from failure to meet the first target). The net proceeds from the issuance were used to retire the $650 million 6.625% Senior Notes due 2025. (F) On June 2, 2021, Constellium SE issued €300 million Sustainability-Linked Senior Notes due 2029 and bearing an interest rate of 3.125%. Deferred arrangement fees were €5 million. Constellium has established two sustainability performance targets (greenhouse gas emissions intensity and recycled metal input). If Constellium does not satisfy the first target for the year ended December 31, 2025, the interest rate will be increased by 0.125%, starting July 15, 2026. If Constellium does not satisfy the second target for the year ended December 31, 2026, the interest rate will be increased by 0.125%, starting July 15, 2027 (in addition to any increase arising from failure to meet the first target). The net proceeds from the issuance were used to retire the $400 million 5.750% Senior Notes due 2024. (G) The Unsecured Revolving Credit Facility of one of our French entities has a €2 million borrowing base and is provided by Bpifrance Financement, a related party.
Schedule of Movement in Borrowings	(in millions of Euros) At June 30, At December 31, At the beginning of the period (January 1) 2,391 2,361 Cash flows Proceeds from issuance of Senior Notes (A) 712 290 Repayment of Senior Notes (A) (863) (200) Repayment of U.S. revolving credit facilities — (129) Proceeds from other borrowings 2 202 Repayments of other borrowings (9) (10) Lease repayments (17) (35) Payment of deferred financing costs (12) (6) Non-cash changes Movement in interest accrued (8) (1) Changes in leases and other loans 8 62 Deferred arrangement fees 13 5 Effects of changes in foreign exchange rates 40 (148) At the end of the period 2,257 2,391
Schedule of Currency Concentration of Total Borrowings	(in millions of Euros) At June 30, At December 31, 2020 U.S. Dollar 1,182 1,602 Euro 1,048 757 Other currencies 27 32 Total borrowings 2,257 2,391

FINANCIAL INSTRUMENTS (Tables)

FINANCIAL INSTRUMENTS (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure of detailed information about financial instruments [abstract]
Schedule of Financial Assets and Liabilities by Categories	At June 30, At December 31, (in millions of Euros) Notes At amortized cost At fair value through profit and loss At fair value through OCI Total At amortized cost At fair value through profit and loss At fair value through OCI Total Cash and cash equivalents 9 290 — — 290 439 — — 439 Trade receivables 10 — — 586 586 — — 341 341 Other financial assets — 73 6 79 3 40 14 57 Total 290 73 592 955 442 40 355 837 At June 30, At December 31, (in millions of Euros) Notes At amortized cost At fair value through profit and loss At fair value through OCI Total At amortized cost At fair value through profit and loss At fair value through OCI Total Trade payables and fixed assets payables 14 981 — — 981 653 — — 653 Borrowings 15 2,257 — — 2,257 2,391 — — 2,391 Other financial liabilities — 34 2 36 — 85 2 87 Total 3,238 34 2 3,274 3,044 85 2 3,131
Schedule of Other Financial Assets and Other Financial Liabilities Positions	At June 30, At December 31, (in millions of Euros) Non-current Current Total Non-current Current Total Aluminium and premium future contracts 8 42 50 1 18 19 Energy future contracts — 1 1 — — — Other future contracts 1 3 4 1 1 2 Currency commercial contracts 7 17 24 16 17 33 Margin call — — — — 3 3 Other financial assets - derivatives 16 63 79 18 39 57 Aluminium and premium future contracts 1 7 8 3 6 9 Other future contracts — 1 1 — 1 1 Currency commercial contracts 2 16 18 4 28 32 Currency net debt derivatives (A) 7 2 9 34 11 45 Other financial liabilities - derivatives 10 26 36 41 46 87 (A) For the six months ended June 30, 2021, forward purchases of $325 million versus the Euro using cross currency basis swaps were bought out before their initial maturity in relation with the refinancing of the Senior Notes. This buy-out generated a €27 million cash outflow which is presented in Other financing activities within the Interim Statement of Cash Flow s.
Schedule of Derivatives Measured at Fair Value	At June 30, At December 31, (in millions of Euros) Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Other financial assets - derivatives 44 35 — 79 20 37 — 57 Other financial liabilities - derivatives 8 28 — 36 9 78 — 87

FINANCIAL RISK MANAGEMENT (Tabl

FINANCIAL RISK MANAGEMENT (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure of detailed information about hedging instruments [table]
Schedule of Effect of Foreign Currency Derivatives Impacts in Consolidated Income Statement and Statement of Comprehensive Income/(Loss)	The table below details the effect of foreign currency derivatives in the Interim Income Statement and the Interim Statement of Comprehensive Income / (Loss): Three months ended June 30, Six months ended June 30, (in millions of Euros) Notes 2021 2020 2021 2020 Derivatives that do not qualify for hedge accounting Included in Other gains and losses - net Realized (losses) / gains on foreign currency derivatives - net 6 (2) — (4) 2 Unrealized gains / (losses) on foreign currency derivatives - net (A) 6 3 (1) 11 (2) Derivatives that qualify for hedge accounting Included in Other comprehensive income / (loss) Unrealized gains / (losses) on foreign currency derivatives - net 2 2 (9) (6) Gains / (losses) reclassified from cash flow hedge reserve to the Interim Income Statement 1 3 1 6 Included in Revenue (B) Realized (losses) / gains on foreign currency derivatives - net 6 — (3) (1) (5) Unrealized gains on foreign currency derivatives - net 6 — 1 — — Derivatives discontinued from hedge accounting Included in Other gains and losses - net Losses reclassified from OCI as a result of hedge accounting discontinuation (C) 6 — (5) — (5) (A) Gains or losses on the hedging instruments are expected to offset losses or gains on the underlying hedged forecasted sales that will be reflected in the future when these sales are recognized. (B) Derivatives that qualify for hedge accounting are included in Revenue when the related customer invoices have been issued. (C) In the six months ended June 30, 2020, we determined that a portion of the hedged forecasted sales for the second half of 2020 and for 2021, to which hedge accounting was applied, was no longer expected to occur. As a result, the fair value of the related derivatives accumulated in equity was reclassified in the Interim Income Statement and resulted a €5 million loss.

PENSIONS AND OTHER POST-EMPLO_2

PENSIONS AND OTHER POST-EMPLOYMENT BENEFIT OBLIGATIONS (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure of employee benefits [Abstract]
Schedule of Sensitivity Analysis and Actuarial Assumptions	At June 30, At December 31, Discount rate Discount rate Switzerland 0.20% 0.00% U.S. — — Hourly pension 2.75% - 2.95% 2.45% - 2.65% Salaried pension 2.85% 2.55% OPEB 2.85% - 3.15% 2.50% - 2.80% Other benefits 2.50% - 2.90% 2.20% - 2.55% France — — Retirements 0.90% 0.50% Other benefits 0.75% 0.40% Germany 0.95% 0.55%
Schedule of Amounts Recognized in the Consolidated Statement of Financial Position	At June 30, At December 31, (in millions of Euros) Pension Benefits Other Benefits Total Pension Benefits Other Benefits Total Present value of funded obligation 741 — 741 772 — 772 Fair value of plan assets (504) — (504) (458) — (458) Deficit of funded plans 237 — 237 314 — 314 Present value of unfunded obligation 131 213 344 134 216 350 Net liability arising from defined benefit obligation 368 213 581 448 216 664
Disclosure Of Defined Benefit Plans Expense Recognised In Income Statement Explanatory	Three months ended June 30, 2021 2020 (in millions of Euros) Pension Benefits Other Benefits Total Pension Benefits Other Benefits Total Service cost Current service cost (6) (2) (8) (5) (1) (6) Past service cost — (2) (2) — (2) (2) Net interest (1) (1) (2) (2) (1) (3) Immediate recognition of gains arising over the year — — — — (1) (1) Administration expenses — — — (1) — (1) Total (7) (5) (12) (8) (5) (13) Six months ended June 30, 2021 2020 (in millions of Euros) Pension Benefits Other Benefits Total Pension Benefits Other Benefits Total Service cost Current service cost (11) (4) (15) (11) (3) (14) Past service cost — (2) (2) — (2) (2) Net interest (2) (2) (4) (3) (3) (6) Immediate recognition of gains arising over the year — 1 1 — — — Administration expenses (1) — (1) (1) — (1) Total (14) (7) (21) (15) (8) (23)
Schedule of Movement in Net Defined Benefit Obligations	At June 30, 2021 Defined benefit obligations Plan Assets Net defined benefit liability (in millions of Euros) Pension benefits Other benefits Total At January 1, 2021 906 216 1,122 (458) 664 Included in the Interim Income Statement Current service cost 11 4 15 — 15 Interest cost / (income) 5 2 7 (3) 4 Past service cost — 2 2 — 2 Immediate recognition of gains arising over the year — (1) (1) — (1) Administration expenses — — — 1 1 Included in the Interim Statement of Comprehensive Income / (loss) Remeasurements due to: —actual return less interest on plan assets — — — (43) (43) —changes in financial assumptions (39) (9) (48) — (48) —changes in demographic assumptions — — — — — —experience losses (1) 1 — — — Effects of changes in foreign exchange rates 5 6 11 (3) 8 Included in the Interim Statement of Cash Flows Benefits paid (17) (9) (26) 15 (11) Contributions by the Group — — — (10) (10) Contributions by the plan participants 2 1 3 (3) — At June 30, 2021 872 213 1,085 (504) 581
Schedule of Net Defined Benefit Obligations by Country	At June 30, At December 31, (in millions of Euros) Defined benefit obligations Plan assets Net defined benefit liability Defined benefit obligations Plan assets Net defined benefit liability France 163 (5) 158 168 (5) 163 Germany 134 (2) 132 143 (1) 142 Switzerland 295 (248) 47 310 (223) 87 United States 492 (249) 243 500 (229) 271 Other countries 1 — 1 1 — 1 Total 1,085 (504) 581 1,122 (458) 664

PROVISIONS (Tables)

PROVISIONS (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure of other provisions [abstract]
Schedule of Changes in Provisions	(in millions of Euros) Close down and environmental remediation costs Restructuring Legal claims Total At January 1, 2021 88 6 27 121 Allowance — 3 1 4 Amounts used — (3) (2) (5) Unused amounts reversed — (1) (3) (4) Unwinding of discounts (2) — — (2) Effects of changes in foreign exchange rates 1 — — 1 At June 30, 2021 87 5 23 115 Current 7 3 10 20 Non-Current 80 2 13 95 Total Provisions 87 5 23 115
Schedule of Legal Claims and Other Costs	(in millions of Euros) At June 30, At December 31, Litigation 17 21 Disease claims 5 5 Other 1 1 Total Provisions for legal claims and other costs 23 27

SHARE CAPITAL (Tables)

SHARE CAPITAL (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure of share capital, reserves and other equity interest [Abstract]
Schedule of Share Capital	(in millions of Euros) Number of shares Share capital Share premium At January 1, 2021 139,962,672 3 420 New shares issued (A) 1,714,694 — — At June 30, 2021 141,677,366 3 420 (A) In the six month ended June 30, 2021, Constellium SE issued and delivered 1,714,694 ordinary shares to certain employees and directors related to share-based compensation plans.

SHARE-BASED COMPENSATION (Table

SHARE-BASED COMPENSATION (Tables)	6 Months Ended
	Jun. 30, 2021
Share-based payment arrangements [Abstract]
Schedule of Inputs to the Model Used for PSUs Granted	The following table lists the inputs to the valuation model used for the PSUs granted in May 2021: May 2021 PSUs Fair value at grant date (in euros) 21.84 Share price at grant date (in euros) 13.90 Dividend yield — Expected volatility (A) 71% Risk-free interest rate (US government bond yield) 0.31% Model used Monte Carlo (A) Volatility in the share prices of the Company and companies included in indices were estimated based on observed historical volatilities over a period equal to the PSU vesting period. The PSUs granted in May 2018 were vested in May 2021 and achieved a TSR performance of 182.9%. 1,161,718 shares related to this vesting were delivered to beneficiaries.
Schedule of Number and Movement of Potential Shares	Performance-Based RSU Restricted Stock Units Equity Award Plans Total potential shares At December 31, 2020 2,594,327 2,231,911 32,912 4,859,150 Granted (A) 614,555 534,499 — 1,149,054 Over-performance (B) 526,551 — — 526,551 Vested (1,161,718) (520,064) (32,912) (1,714,694) Forfeited (C) (9,970) (30,815) — (40,785) At June 30, 2021 2,563,745 2,215,531 — 4,779,276 (A) For PSUs, the number of potential shares granted is presented using a vesting multiplier of 100%. (B) When the achievement of TSR performance exceeds the vesting multiplier of 100%, the additional potential shares are presented as over-performance shares. (C) For potential shares related to PSUs, 9,970 were forfeited following the departure of certain beneficiaries and none were forfeited in relation to the non-fulfilment of performance conditions.

GENERAL INFORMATION (Details)

GENERAL INFORMATION (Details) employee in Thousands	Jun. 30, 2021employeefacilitysitecenter
Disclosure of general information [abstract]
Number of production facilities | facility	29
Number of R&D centers | center	3
Number of administrative centers | site	3
Number of employees | employee	12

SUMMARY OF SIGNIFICANT ACCOUN_4

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Disclosure of Foreign Exchange Rates (Details)	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
U.S. Dollars
Disclosure of foreign exchange rates [line items]
Average rates	1.2052	1.1018
Closing rates	1.1884		1.2271
Swiss Francs
Disclosure of foreign exchange rates [line items]
Average rates	1.0945	1.0641
Closing rates	1.0980		1.0802
Czech Koruna
Disclosure of foreign exchange rates [line items]
Average rates	25.8508	26.2970
Closing rates	25.4880		26.2420

REVENUE - Disaggregation of Rev

REVENUE - Disaggregation of Revenue by Product Line (Details) - EUR (€) € in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disclosure of products and services [line items]
Total Revenue	€ 1,518	€ 1,031	€ 2,859	€ 2,468
Packaging rolled products
Disclosure of products and services [line items]
Total Revenue	648	456	1,167	980
Automotive rolled products
Disclosure of products and services [line items]
Total Revenue	213	88	421	281
Specialty and other thin-rolled products
Disclosure of products and services [line items]
Total Revenue	43	20	80	52
Aerospace rolled products
Disclosure of products and services [line items]
Total Revenue	100	142	187	365
Transportation, industry, defense and other rolled products
Disclosure of products and services [line items]
Total Revenue	174	105	321	231
Automotive extruded products
Disclosure of products and services [line items]
Total Revenue	176	96	377	295
Other extruded products
Disclosure of products and services [line items]
Total Revenue	€ 164	€ 124	€ 306	€ 264

REVENUE - Disaggregation of R_2

REVENUE - Disaggregation of Revenue by Destination of Shipment (Details) - EUR (€) € in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disclosure of geographical areas [line items]
Total Revenue	€ 1,518	€ 1,031	€ 2,859	€ 2,468
Germany
Disclosure of geographical areas [line items]
Total Revenue	373	192	711	479
France
Disclosure of geographical areas [line items]
Total Revenue	120	67	224	188
United Kingdom
Disclosure of geographical areas [line items]
Total Revenue	42	39	79	108
Switzerland
Disclosure of geographical areas [line items]
Total Revenue	17	15	30	27
Other Europe
Disclosure of geographical areas [line items]
Total Revenue	308	201	587	476
Total Europe
Disclosure of geographical areas [line items]
Total Revenue	860	514	1,631	1,278
United States
Disclosure of geographical areas [line items]
Total Revenue	559	413	1,040	974
Asia and Other Pacific
Disclosure of geographical areas [line items]
Total Revenue	43	61	79	118
All Other
Disclosure of geographical areas [line items]
Total Revenue	€ 56	€ 43	€ 109	€ 98

OPERATING SEGMENT INFORMATION -

OPERATING SEGMENT INFORMATION - Narrative (Details)	Jun. 30, 2021segment
Disclosure of operating segments [abstract]
Number of reportable segments	3

OPERATING SEGMENT INFORMATION_2

OPERATING SEGMENT INFORMATION - Segment Revenue (Details) - EUR (€) € in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disclosure of operating segments [line items]
Revenue	€ 1,518	€ 1,031	€ 2,859	€ 2,468
P&ARP
Disclosure of operating segments [line items]
Revenue	904	564	1,668	1,313
A&T
Disclosure of operating segments [line items]
Revenue	274	247	508	596
AS&I
Disclosure of operating segments [line items]
Revenue	340	220	683	559
Segment revenue
Disclosure of operating segments [line items]
Revenue	1,539	1,037	2,900	2,490
Segment revenue | P&ARP
Disclosure of operating segments [line items]
Revenue	907	565	1,673	1,317
Segment revenue | A&T
Disclosure of operating segments [line items]
Revenue	287	250	532	609
Segment revenue | AS&I
Disclosure of operating segments [line items]
Revenue	345	222	695	564
Inter-segment elimination
Disclosure of operating segments [line items]
Revenue	(21)	(6)	(41)	(22)
Inter-segment elimination | P&ARP
Disclosure of operating segments [line items]
Revenue	(3)	(1)	(5)	(4)
Inter-segment elimination | A&T
Disclosure of operating segments [line items]
Revenue	(13)	(3)	(24)	(13)
Inter-segment elimination | AS&I
Disclosure of operating segments [line items]
Revenue	€ (5)	€ (2)	€ (12)	€ (5)

OPERATING SEGMENT INFORMATION_3

OPERATING SEGMENT INFORMATION - Segment Adjusted EBITDA and reconciliation of Adjusted EBITDA to Net Income (Details) - EUR (€) € in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Disclosure of segment adjusted EBITDA and reconciliation of adjusted EBITDA to net income [line items]
Adjusted EBITDA	€ 170	€ 81	€ 291	€ 228
Metal price lag	54	(25)	85	(40)
Start-up and development costs	0	(2)	0	(4)
Share based compensation costs	(3)	(5)	(7)	(8)
Losses on pension plan amendments	(2)	(2)	(2)	(2)
Depreciation and amortization	(65)	(66)	(128)	(132)
Impairment of assets	0	(5)	0	(5)
Restructuring costs	(2)	(11)	(3)	(11)
Unrealized exchange (losses) / gains from the remeasurement of monetary assets and liabilities – net	(1)	1	1	(1)
Other	0	(10)	0	(10)
Income / (loss) from operations	167	(1)	281	5
Finance costs - net	(37)	(42)	(92)	(87)
Income / (loss) before tax	130	(43)	189	(82)
Income tax (expense) / benefit	(22)	11	(33)	19
Net income / (loss)	108	(32)	156	(63)	€ (17)
Losses reclassified from OCI as a result of hedge accounting discontinuation	0	5	0	5
Unrealized gains / (losses) on derivatives	16	43	44	(10)
COVID-19
Disclosure of segment adjusted EBITDA and reconciliation of adjusted EBITDA to net income [line items]
Procurement penalties and termination fees				(5)
Losses reclassified from OCI as a result of hedge accounting discontinuation				5
P&ARP
Disclosure of segment adjusted EBITDA and reconciliation of adjusted EBITDA to net income [line items]
Adjusted EBITDA	94	58	162	124
A&T
Disclosure of segment adjusted EBITDA and reconciliation of adjusted EBITDA to net income [line items]
Adjusted EBITDA	42	31	61	83
AS&I
Disclosure of segment adjusted EBITDA and reconciliation of adjusted EBITDA to net income [line items]
Adjusted EBITDA	41	(1)	79	33
H&C
Disclosure of segment adjusted EBITDA and reconciliation of adjusted EBITDA to net income [line items]
Adjusted EBITDA	€ (7)	€ (7)	€ (11)	€ (12)

OPERATING SEGMENT INFORMATION_4

OPERATING SEGMENT INFORMATION - Segment Capital Expenditures (Details) - EUR (€) € in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Disclosure of operating segments [line items]
Capital expenditures	€ (74)	€ (100)
P&ARP
Disclosure of operating segments [line items]
Capital expenditures	(27)	(38)
A&T
Disclosure of operating segments [line items]
Capital expenditures	(21)	(25)
AS&I
Disclosure of operating segments [line items]
Capital expenditures	(24)	(35)
H&C
Disclosure of operating segments [line items]
Capital expenditures	€ (2)	€ (2)

OPERATING SEGMENT INFORMATION_5

OPERATING SEGMENT INFORMATION - Segment Assets (Details) - EUR (€) € in Millions	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Disclosure of operating segments [line items]
Total Assets	€ 4,455	€ 4,129
Deferred tax assets	162	193
Cash and cash equivalents	290	439	€ 378	€ 184
Segment revenue
Disclosure of operating segments [line items]
Total Assets	3,924	3,440
Segment revenue | P&ARP
Disclosure of operating segments [line items]
Total Assets	1,983	1,733
Segment revenue | A&T
Disclosure of operating segments [line items]
Total Assets	857	765
Segment revenue | AS&I
Disclosure of operating segments [line items]
Total Assets	698	668
Segment revenue | H&C
Disclosure of operating segments [line items]
Total Assets	386	274
Unallocated
Disclosure of operating segments [line items]
Deferred tax assets	162	193
Cash and cash equivalents	290	439
Other financial assets	€ 79	€ 57

OTHER GAINS AND LOSSES_NET (Det

OTHER GAINS AND LOSSES—NET (Details) - EUR (€) € in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Analysis of income and expense [abstract]
Realized (losses) / gains on derivatives	€ 31	€ (32)	€ 45	€ (44)
Losses reclassified from OCI as a result of hedge accounting discontinuation	0	(5)	0	(5)
Unrealized gains / (losses) on derivatives at fair value through profit and loss—net	17	43	45	(10)
Unrealized exchange (losses) / gains from the remeasurement of monetary assets and liabilities – net	(1)	1	1	(1)
Impairment of assets	0	(5)	0	(5)
Restructuring costs	(2)	(11)	(3)	(11)
Losses on pension plan amendments	(2)	(2)	(2)	(2)
Other	1	0	1	(1)
Total other gains and losses - net	44	(11)	87	(79)
Analysis of income and expense [line items]
Impairment of assets	0	(5)	0	(5)
Expense of restructuring activities	€ 2	€ 11	€ 3	11
COVID-19
Analysis of income and expense [abstract]
Losses reclassified from OCI as a result of hedge accounting discontinuation				(5)
A&T and AC&I | COVID-19
Analysis of income and expense [abstract]
Impairment of assets				(5)
Analysis of income and expense [line items]
Impairment of assets				€ (5)

CURRENCY GAINS _ (LOSSES) - Cur

CURRENCY GAINS / (LOSSES) - Currency Gains and Losses Included in Income from Operations (Details) € in Millions, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2021EUR (€)	Jun. 30, 2021USD ($)	Jun. 30, 2020EUR (€)	Jun. 30, 2020USD ($)	Jun. 30, 2021EUR (€)	Jun. 30, 2021USD ($)	Jun. 30, 2020EUR (€)	Jun. 30, 2020USD ($)
Analysis of income and expense [line items]
Total	€ 0	$ 0	€ (6)	$ (6)	€ 7	$ 7	€ (10)	$ (10)
Realized exchange losses on foreign currency derivatives - net	(2)		(3)		(5)		(3)
Losses reclassified from OCI as a result of hedge accounting discontinuation	0		(5)		0		(5)
Unrealized gains / (losses) on foreign currency derivatives - net	3		0		11		(2)
Exchange (losses) / gains from the remeasurement of monetary assets and liabilities - net	(1)		2		1		0
Included in Revenue
Analysis of income and expense [line items]
Total	0		(2)		(1)		(5)
Included in Cost of sales
Analysis of income and expense [line items]
Total	0		1		0		1
Included in Other gains and losses - net
Analysis of income and expense [line items]
Total	€ 0		€ (5)		€ 8		€ (6)

FINANCE COSTS_NET (Details)

FINANCE COSTS—NET (Details) - EUR (€) € in Millions	Jun. 02, 2021	Feb. 24, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Analysis of income and expense [line items]
Interest expense on borrowings			€ (26)	€ (32)	€ (56)	€ (64)
Interest expense on leases			(2)	(2)	(5)	(5)
Interest cost on pension and other benefits			(2)	(3)	(4)	(6)
Expenses on factoring arrangements			(2)	(3)	(4)	(6)
Net loss on settlement of debt			(6)	0	(23)	0
Realized and unrealized (losses) / gains on debt derivatives at fair value			(15)	(7)	0	1
Realized and unrealized exchange (losses) / gains on financing activities - net			16	8	0	(3)
Other finance expenses			(1)	(4)	(1)	(5)
Capitalized borrowing costs			1	1	1	1
Finance expenses			(37)	(42)	(92)	(87)
Finance costs - net			€ (37)	€ (42)	(92)	(87)
Redemption of senior notes					€ 863	€ 200	€ 200
Capitalization rate					5.00%	6.00%
Constellium SE Senior Notes
Analysis of income and expense [line items]
Interest expense on debt instruments issued					€ 50	€ 57
Borrowing costs recognised as expense					€ 2	€ 3
Senior Unsecured Notes due 2025
Analysis of income and expense [line items]
Redemption of senior notes		€ 650
Nominal rate		6.625%			6.625%
Debt redemption fees		€ 9
Write off of deferred debt costs		€ 8
Senior Unsecured Notes due 2024
Analysis of income and expense [line items]
Redemption of senior notes	€ 400
Nominal rate	5.75%				5.75%
Debt redemption fees	€ 3
Write off of deferred debt costs	€ 3

CASH AND CASH EQUIVALENTS (Deta

CASH AND CASH EQUIVALENTS (Details) - EUR (€) € in Millions	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Disclosure of cash and cash equivalents [line Items]
Cash in bank and on hand	€ 290	€ 439	€ 378	€ 184
Cash subject to restrictions		€ 26
Subsidiaries in capital control restrictions countries
Disclosure of cash and cash equivalents [line Items]
Cash subject to restrictions	€ 25

TRADE RECEIVABLES AND OTHER (De

TRADE RECEIVABLES AND OTHER (Details) - EUR (€) € in Millions	Jun. 30, 2021	Dec. 31, 2020
Non-current
Trade receivables	€ 0	€ 0
Income tax receivables	39	34
Other tax receivables	0	0
Contract assets	18	23
Prepaid expenses	1	1
Other	11	10
Total other receivables	69	68
Total trade receivables and other	69	68
Current
Trade receivables	586	341
Income tax receivables	5	15
Other tax receivables	45	33
Contract assets	2	2
Prepaid expenses	21	6
Other	10	9
Total other receivables	83	65
Total trade receivables and other	669	406
Cost
Non-current
Trade receivables	0	0
Current
Trade receivables	590	345
Impairment
Non-current
Trade receivables	0	0
Current
Trade receivables	€ (4)	€ (4)

TRADE RECEIVABLES AND OTHER - C

TRADE RECEIVABLES AND OTHER - Contract Assets (Details) - EUR (€) € in Millions	Jun. 30, 2021	Dec. 31, 2020
Disclosure of disaggregation of revenue from contracts with customers [line items]
Contact assets, Non-current	€ 18	€ 23
Contract assets, Current	2	2
Unbilled tooling costs
Disclosure of disaggregation of revenue from contracts with customers [line items]
Contact assets, Non-current	5	9
Contract assets, Current	0	0
Other
Disclosure of disaggregation of revenue from contracts with customers [line items]
Contact assets, Non-current	13	14
Contract assets, Current	€ 2	€ 2

TRADE RECEIVABLES AND OTHER - A

TRADE RECEIVABLES AND OTHER - Aging of Total Trade Receivables - Net (Details) - EUR (€) € in Millions	Jun. 30, 2021	Dec. 31, 2020
Trade receivables [line items]
Trade receivables	€ 586	€ 341
Not past due
Trade receivables [line items]
Trade receivables	577	333
1 – 30 days past due
Trade receivables [line items]
Trade receivables	8	7
31 – 60 days past due
Trade receivables [line items]
Trade receivables	1	1
61 – 90 days past due
Trade receivables [line items]
Trade receivables	0	0
Greater than 90 days past due
Trade receivables [line items]
Trade receivables	€ 0	€ 0

TRADE RECEIVABLES AND OTHER - N

TRADE RECEIVABLES AND OTHER - Narrative (Details)	6 Months Ended
	Jun. 30, 2021EUR (€)	Jun. 30, 2021USD ($)	Jun. 30, 2020EUR (€)	Dec. 31, 2020EUR (€)
Disclosure of trade and other receivables [line items]
Allowance for impairment on trade receivables recognized	€ (400,000)		€ (400,000)
Trade receivables	586,000,000			€ 341,000,000
Total factored assets	587,000,000			514,000,000
Factored assets derecognized	384,000,000			398,000,000
Debt due factor	1,000,000			€ 0
Impairment
Disclosure of trade and other receivables [line items]
Trade receivables	0		€ 0
United States | Factoring of receivables | Muscle Shoals factoring facility
Disclosure of trade and other receivables [line items]
Factoring maximum capacity | $		$ 300,000,000
United States | Factoring of receivables | Constellium automotive
Disclosure of trade and other receivables [line items]
Factoring maximum capacity | $		$ 25,000,000
France | Factoring of receivables
Disclosure of trade and other receivables [line items]
Factoring maximum capacity	255,000,000
France | Factoring Receivable, Recourse Line
Disclosure of trade and other receivables [line items]
Factoring maximum capacity	20,000,000
Germany, Switzerland and Czech Republic | Factoring of receivables
Disclosure of trade and other receivables [line items]
Factoring maximum capacity	€ 150,000,000

TRADE RECEIVABLES AND OTHER -_2

TRADE RECEIVABLES AND OTHER - Carrying Amounts of Total Trade Receivables - Net by Currency (Details) - EUR (€) € in Millions	Jun. 30, 2021	Dec. 31, 2020
Trade receivables [line items]
Trade receivables	€ 586	€ 341
Euro
Trade receivables [line items]
Trade receivables	277	143
U.S. Dollars
Trade receivables [line items]
Trade receivables	289	181
Swiss Francs
Trade receivables [line items]
Trade receivables	7	6
Other currencies
Trade receivables [line items]
Trade receivables	€ 13	€ 11

INVENTORIES (Details)

INVENTORIES (Details) - EUR (€) € in Millions	Jun. 30, 2021	Dec. 31, 2020
Subclassifications of assets, liabilities and equities [abstract]
Finished goods	€ 196	€ 149
Work in progress	428	280
Raw materials	137	118
Stores and supplies	87	80
Inventories write down	(46)	(45)
Total inventories	€ 802	€ 582

PROPERTY, PLANT AND EQUIPMENT_2

PROPERTY, PLANT AND EQUIPMENT (Details) € in Millions	6 Months Ended
	Jun. 30, 2021EUR (€)
Reconciliation of changes in property, plant and equipment [abstract]
Beginning balance	€ 1,906
Additions	82
Disposals	(1)
Depreciation expense	(123)
Transfer and other changes	1
Effect of changes in foreign exchange rates	30
Ending balance	1,895
Cost
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	3,387
Less accumulated depreciation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	(1,492)
Land and Property Rights
Reconciliation of changes in property, plant and equipment [abstract]
Beginning balance	20
Additions	0
Disposals	0
Depreciation expense	0
Transfer and other changes	0
Effect of changes in foreign exchange rates	1
Ending balance	21
Land and Property Rights | Cost
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	37
Land and Property Rights | Less accumulated depreciation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	(16)
Buildings
Reconciliation of changes in property, plant and equipment [abstract]
Beginning balance	379
Additions	4
Disposals	0
Depreciation expense	(14)
Transfer and other changes	1
Effect of changes in foreign exchange rates	5
Ending balance	375
Buildings | Cost
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	573
Buildings | Less accumulated depreciation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	(198)
Machinery and Equipment
Reconciliation of changes in property, plant and equipment [abstract]
Beginning balance	1,361
Additions	23
Disposals	(1)
Depreciation expense	(104)
Transfer and other changes	45
Effect of changes in foreign exchange rates	23
Ending balance	1,347
Machinery and Equipment | Cost
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	2,579
Machinery and Equipment | Less accumulated depreciation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	(1,232)
Construction Work in Progress
Reconciliation of changes in property, plant and equipment [abstract]
Beginning balance	132
Additions	54
Disposals	0
Depreciation expense	(1)
Transfer and other changes	(48)
Effect of changes in foreign exchange rates	1
Ending balance	138
Construction Work in Progress | Cost
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	147
Construction Work in Progress | Less accumulated depreciation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	(9)
Other
Reconciliation of changes in property, plant and equipment [abstract]
Beginning balance	14
Additions	1
Disposals	0
Depreciation expense	(4)
Transfer and other changes	3
Effect of changes in foreign exchange rates	0
Ending balance	14
Other | Cost
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	51
Other | Less accumulated depreciation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	€ (37)

PROPERTY, PLANT AND EQUIPMENT -

PROPERTY, PLANT AND EQUIPMENT - Right of Use Assets (Details) € in Millions	6 Months Ended
	Jun. 30, 2021EUR (€)
Reconciliation of changes in property, plant and equipment [abstract]
Beginning balance	€ 1,906
Additions	82
Depreciation expense	(123)
Transfer and other changes	1
Effect of changes in foreign exchange rates	30
Ending balance	1,895
Cost
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	3,387
Less accumulated depreciation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	(1,492)
Buildings
Reconciliation of changes in property, plant and equipment [abstract]
Beginning balance	379
Additions	4
Depreciation expense	(14)
Transfer and other changes	1
Effect of changes in foreign exchange rates	5
Ending balance	375
Buildings | Cost
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	573
Buildings | Less accumulated depreciation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	(198)
Machinery and Equipment
Reconciliation of changes in property, plant and equipment [abstract]
Beginning balance	1,361
Additions	23
Depreciation expense	(104)
Transfer and other changes	45
Effect of changes in foreign exchange rates	23
Ending balance	1,347
Machinery and Equipment | Cost
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	2,579
Machinery and Equipment | Less accumulated depreciation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	(1,232)
Other
Reconciliation of changes in property, plant and equipment [abstract]
Beginning balance	14
Additions	1
Depreciation expense	(4)
Transfer and other changes	3
Effect of changes in foreign exchange rates	0
Ending balance	14
Other | Cost
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	51
Other | Less accumulated depreciation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	(37)
Right-of-use assets
Reconciliation of changes in property, plant and equipment [abstract]
Beginning balance	186
Additions	7
Depreciation expense	(16)
Transfer and other changes	(1)
Effect of changes in foreign exchange rates	2
Ending balance	178
Right-of-use assets | Cost
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	289
Right-of-use assets | Less accumulated depreciation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	(111)
Right-of-use assets | Buildings
Reconciliation of changes in property, plant and equipment [abstract]
Beginning balance	112
Additions	4
Depreciation expense	(6)
Transfer and other changes	0
Effect of changes in foreign exchange rates	1
Ending balance	111
Right-of-use assets | Buildings | Cost
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	147
Right-of-use assets | Buildings | Less accumulated depreciation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	(36)
Right-of-use assets | Machinery and Equipment
Reconciliation of changes in property, plant and equipment [abstract]
Beginning balance	72
Additions	3
Depreciation expense	(10)
Transfer and other changes	(1)
Effect of changes in foreign exchange rates	1
Ending balance	65
Right-of-use assets | Machinery and Equipment | Cost
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	138
Right-of-use assets | Machinery and Equipment | Less accumulated depreciation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	(73)
Right-of-use assets | Other
Reconciliation of changes in property, plant and equipment [abstract]
Beginning balance	2
Additions	0
Depreciation expense	0
Transfer and other changes	0
Effect of changes in foreign exchange rates	0
Ending balance	2
Right-of-use assets | Other | Cost
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	4
Right-of-use assets | Other | Less accumulated depreciation and impairment
Reconciliation of changes in property, plant and equipment [abstract]
Ending balance	€ (2)

PROPERTY, PLANT AND EQUIPMENT_3

PROPERTY, PLANT AND EQUIPMENT - Narrative (Details) - EUR (€) € in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Property, plant and equipment [abstract]
Expense related to short-term leases, low value asset leases and variable lease still recognized as operating expenses	€ 5	€ 6

INTANGIBLE ASSETS AND GOODWIL_2

INTANGIBLE ASSETS AND GOODWILL - Changes in Intangible Assets and Goodwill (Details) € in Millions	6 Months Ended
	Jun. 30, 2021EUR (€)
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	€ 61
Additions	2
Amortization expense	(5)
Transfer	0
Effect of changes in foreign exchange rates	1
Intangible assets (excluding goodwill), ending balance	59
Changes in goodwill [abstract]
Goodwill, beginning balance	417
Effect of changes in foreign exchange rates	13
Goodwill, ending balance	430
Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	214
Changes in goodwill [abstract]
Goodwill, ending balance	430
Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	(155)
Technology
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	18
Additions	0
Amortization expense	(1)
Transfer	0
Effect of changes in foreign exchange rates	1
Intangible assets (excluding goodwill), ending balance	18
Technology | Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	82
Technology | Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	(64)
Computer Software
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	15
Additions	0
Amortization expense	(4)
Transfer	4
Effect of changes in foreign exchange rates	0
Intangible assets (excluding goodwill), ending balance	15
Computer Software | Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	80
Computer Software | Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	(65)
Customer relationships
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	13
Additions	0
Amortization expense	0
Transfer	0
Effect of changes in foreign exchange rates	0
Intangible assets (excluding goodwill), ending balance	13
Customer relationships | Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	38
Customer relationships | Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	(25)
Work in Progress
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	13
Additions	2
Amortization expense	0
Transfer	(4)
Effect of changes in foreign exchange rates	0
Intangible assets (excluding goodwill), ending balance	11
Work in Progress | Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	12
Work in Progress | Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	(1)
Other
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	2
Additions	0
Amortization expense	0
Transfer	0
Effect of changes in foreign exchange rates	0
Intangible assets (excluding goodwill), ending balance	2
Other | Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	2
Other | Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	€ 0

TRADE PAYABLES AND OTHER (Detai

TRADE PAYABLES AND OTHER (Details) - EUR (€) € in Millions	Jun. 30, 2021	Dec. 31, 2020
Non-current
Trade payables	€ 0	€ 0
Fixed assets payables	0	0
Employees' entitlements	0	0
Taxes payable other than income tax	0	0
Contract liabilities and other liabilities to customers	3	3
Other payables	29	29
Total other	32	32
Total Trade payables and other	32	32
Current
Trade payables	950	626
Fixed assets payables	31	27
Employees' entitlements	165	143
Taxes payable other than income tax	29	15
Contract liabilities and other liabilities to customers	62	81
Other payables	18	13
Total other	305	279
Total Trade payables and other	€ 1,255	€ 905

TRADE PAYABLES AND OTHER - Cont

TRADE PAYABLES AND OTHER - Contract Liabilities (Details) - EUR (€) € in Millions	Jun. 30, 2021	Dec. 31, 2020
Disclosure of disaggregation of contract liabilities with customers [line items]
Non-current	€ 3	€ 3
Current	62	81
Deferred tooling revenue
Disclosure of disaggregation of contract liabilities with customers [line items]
Non-current	2	2
Current	0	0
Advance payment from customers
Disclosure of disaggregation of contract liabilities with customers [line items]
Non-current	0	0
Current	1	2
Unrecognized variable consideration
Disclosure of disaggregation of contract liabilities with customers [line items]
Non-current	1	1
Current	59	72
Other
Disclosure of disaggregation of contract liabilities with customers [line items]
Non-current	0	0
Current	€ 2	€ 7

TRADE PAYABLES AND OTHER - Narr

TRADE PAYABLES AND OTHER - Narrative (Details) - EUR (€) € in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Trade and other payables [abstract]
Revenue recognized related to contract liabilities	€ 23	€ 14
Deferred revenue related to contract liabilities	€ 20	€ 25

BORROWINGS - Borrowings by Natu

BORROWINGS - Borrowings by Nature (Details)	Jun. 02, 2021EUR (€)target	Feb. 24, 2021EUR (€)target	Jun. 30, 2021EUR (€)	Jun. 30, 2020EUR (€)	Dec. 31, 2020EUR (€)	Jun. 30, 2021USD ($)	Jun. 30, 2021CHF (SFr)	Jun. 02, 2021USD ($)target	Feb. 24, 2021USD ($)target	Dec. 31, 2019EUR (€)
Disclosure of detailed information about borrowings [line items]
Nominal value			€ 2,260,000,000
Gross lease liabilities			186,000,000
Arrangement fees			(27,000,000)
Accrued interests			24,000,000
Accrued interest lease liabilities			1,000,000
Total Borrowings			2,257,000,000		€ 2,391,000,000					€ 2,361,000,000
Lease liabilities			187,000,000		195,000,000
Non-current borrowings			1,995,000,000		2,299,000,000
Current borrowings			262,000,000		92,000,000
Repurchase of senior notes			863,000,000	€ 200,000,000	200,000,000
Secured Pan-U.S. ABL (due 2026)
Disclosure of detailed information about borrowings [line items]
Total Borrowings			0		0
Secured U.S. DDTL (due 2022)
Disclosure of detailed information about borrowings [line items]
Total Borrowings			0		0
Secured French PGE French Facility (due 2022)
Disclosure of detailed information about borrowings [line items]
Nominal value			180,000,000			$ 180,000,000
Arrangement fees			0
Accrued interests			0
Total Borrowings			€ 180,000,000		180,000,000
Secured German Facility (due 2022)
Disclosure of detailed information about borrowings [line items]
Nominal rate			2.00%
Total Borrowings			€ 0		0
Secured Inventory Facility (due 2023)
Disclosure of detailed information about borrowings [line items]
Total Borrowings			0		0
Senior Unsecured Notes due 2024
Disclosure of detailed information about borrowings [line items]
Nominal value			€ 0			400,000,000
Nominal rate	5.75%		5.75%
Arrangement fees			€ 0
Accrued interests			0
Total Borrowings			0		325,000,000
Repurchase of senior notes	€ 400,000,000
Senior Unsecured Notes due 2025
Disclosure of detailed information about borrowings [line items]
Nominal value			€ 0			650,000,000
Nominal rate		6.625%	6.625%
Arrangement fees			€ 0
Accrued interests			0
Total Borrowings			0		534,000,000
Repurchase of senior notes		€ 650,000,000
Senior Unsecured Notes due 2026
Disclosure of detailed information about borrowings [line items]
Nominal value			€ 421,000,000			500,000,000
Nominal rate			5.875%
Arrangement fees			€ (5,000,000)
Accrued interests			9,000,000
Total Borrowings			425,000,000		411,000,000
Senior Unsecured Note due 2026
Disclosure of detailed information about borrowings [line items]
Nominal value			€ 400,000,000
Nominal rate			4.25%
Arrangement fees			€ (4,000,000)
Accrued interests			6,000,000
Total Borrowings			402,000,000		401,000,000
Senior Unscured Notes due 2028
Disclosure of detailed information about borrowings [line items]
Nominal value			€ 274,000,000			325,000,000
Nominal rate			5.625%
Arrangement fees			€ (6,000,000)
Accrued interests			1,000,000
Total Borrowings			269,000,000		260,000,000
Sustainability-Linked Senior Notes Issued February 2021 Due 2029
Disclosure of detailed information about borrowings [line items]
Nominal value			€ 421,000,000			500,000,000			$ 500,000,000
Nominal rate		3.75%	3.75%
Arrangement fees		€ (7,000,000)	€ (7,000,000)
Accrued interests			5,000,000
Total Borrowings			419,000,000		0
Number of sustainability performance targets | target		2							2
Sustainability-Linked Senior Notes Issued February 2021 Due 2029 | Starting April 15, 2026
Disclosure of detailed information about borrowings [line items]
Increase in nominal rate		0.00125
Sustainability-Linked Senior Notes Issued February 2021 Due 2029 | Starting April 15, 2027
Disclosure of detailed information about borrowings [line items]
Increase in nominal rate		0.00125
Sustainability-Link Senior Notes Issued June 2021 due 2029
Disclosure of detailed information about borrowings [line items]
Nominal value			€ 300,000,000			$ 300,000,000		$ 300,000,000
Nominal rate	3.125%		3.125%
Arrangement fees	€ (5,000,000)		€ (5,000,000)
Accrued interests			1,000,000
Total Borrowings			296,000,000		0
Number of sustainability performance targets | target	2							2
Sustainability-Link Senior Notes Issued June 2021 due 2029 | Starting April 15, 2026
Disclosure of detailed information about borrowings [line items]
Increase in nominal rate	0.00125
Sustainability-Link Senior Notes Issued June 2021 due 2029 | Starting April 15, 2027
Disclosure of detailed information about borrowings [line items]
Increase in nominal rate	0.00125
Unsecured Revolving Credit Facility (due 2029)
Disclosure of detailed information about borrowings [line items]
Total Borrowings			0		0
Unsecured Revolving Credit Facility (due 2029) | BPI France
Disclosure of detailed information about borrowings [line items]
Borrowing capacity			2,000,000
Unsecured Swiss Facility (due 2025)
Disclosure of detailed information about borrowings [line items]
Nominal value			€ 16,000,000				SFr 17,000,000
Nominal rate			1.175%
Arrangement fees			€ 0
Accrued interests			0
Total Borrowings			€ 16,000,000		18,000,000
Unsecured German Facilities (due 2022)
Disclosure of detailed information about borrowings [line items]
Nominal rate			2.12%
Total Borrowings			€ 0		0
Other loans
Disclosure of detailed information about borrowings [line items]
Nominal value			62,000,000
Arrangement fees			0
Accrued interests			1,000,000
Total Borrowings			63,000,000		€ 67,000,000
Financing Arrangements
Disclosure of detailed information about borrowings [line items]
Total Borrowings			€ 42,000,000

BORROWINGS - Movement in Borrow

BORROWINGS - Movement in Borrowings (Details)	Jun. 02, 2021EUR (€)	Feb. 24, 2021EUR (€)	Jun. 30, 2021EUR (€)	Jun. 30, 2020EUR (€)	Dec. 31, 2020EUR (€)	Jun. 30, 2021USD ($)	Jun. 02, 2021USD ($)	Feb. 24, 2021USD ($)
Disclosure of detailed information about borrowings [line items]
At the beginning of the period (January 1)			€ 2,391,000,000	€ 2,361,000,000	€ 2,361,000,000
Cash flows
Proceeds from issuance of Senior Notes			712,000,000	290,000,000	290,000,000
Repayments of Senior Notes			(863,000,000)	(200,000,000)	(200,000,000)
Repayments of U.S. revolving credit facility			0		(129,000,000)
Proceeds from other borrowings			2,000,000	207,000,000	202,000,000
Repayments of other borrowings			(9,000,000)	€ (4,000,000)	(10,000,000)
Lease repayments			(17,000,000)		(35,000,000)
Payment of deferred financing costs			(12,000,000)		(6,000,000)
Non-cash changes
Movement in interest accrued			(8,000,000)		(1,000,000)
Changes in leases and other loans			8,000,000		62,000,000
Deferred arrangement fees			13,000,000		5,000,000
Effects of changes in foreign exchange rates			40,000,000		(148,000,000)
At the end of the period			2,257,000,000		2,391,000,000
Nominal value			2,260,000,000
Sustainability-Linked Senior Notes Issued February 2021 Due 2029
Disclosure of detailed information about borrowings [line items]
At the beginning of the period (January 1)			0
Non-cash changes
At the end of the period			419,000,000		0
Nominal value			€ 421,000,000			$ 500,000,000		$ 500,000,000
Nominal rate		3.75%	3.75%
Senior Unsecured Notes due 2025
Disclosure of detailed information about borrowings [line items]
At the beginning of the period (January 1)			€ 534,000,000
Cash flows
Repayments of Senior Notes		€ (650,000,000)
Non-cash changes
At the end of the period			0		534,000,000
Nominal value			€ 0			650,000,000
Nominal rate		6.625%	6.625%
Sustainability-Link Senior Notes Issued June 2021 due 2029
Disclosure of detailed information about borrowings [line items]
At the beginning of the period (January 1)			€ 0
Non-cash changes
At the end of the period			296,000,000		0
Nominal value			€ 300,000,000			300,000,000	$ 300,000,000
Nominal rate	3.125%		3.125%
Senior Unsecured Notes due 2024
Disclosure of detailed information about borrowings [line items]
At the beginning of the period (January 1)			€ 325,000,000
Cash flows
Repayments of Senior Notes	€ (400,000,000)
Non-cash changes
At the end of the period			0		€ 325,000,000
Nominal value			€ 0			$ 400,000,000
Nominal rate	5.75%		5.75%

BORROWINGS - Currency Concentra

BORROWINGS - Currency Concentration of Total Borrowings (Details) - EUR (€) € in Millions	Jun. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about borrowings [line items]
Total Borrowings	€ 2,257	€ 2,391	€ 2,361
U.S. Dollars
Disclosure of detailed information about borrowings [line items]
Total Borrowings	1,182	1,602
Euro
Disclosure of detailed information about borrowings [line items]
Total Borrowings	1,048	757
Other currencies
Disclosure of detailed information about borrowings [line items]
Total Borrowings	€ 27	€ 32

FINANCIAL INSTRUMENTS - Financi

FINANCIAL INSTRUMENTS - Financial Assets and Liabilities by Categories (Details) - EUR (€) € in Millions	Jun. 30, 2021	Dec. 31, 2020
Disclosure of detailed information about financial instruments [line items]
Financial assets	€ 955	€ 837
Financial liabilities	3,274	3,131
Trade payables and fixed assets payables
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	981	653
Borrowings
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	2,257	2,391
Other financial liabilities
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	36	87
At amortized cost
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	3,238	3,044
At amortized cost | Trade payables and fixed assets payables
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	981	653
At amortized cost | Borrowings
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	2,257	2,391
At amortized cost | Other financial liabilities
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	0	0
At fair value through profit and loss
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	34	85
At fair value through profit and loss | Trade payables and fixed assets payables
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	0	0
At fair value through profit and loss | Borrowings
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	0	0
At fair value through profit and loss | Other financial liabilities
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	34	85
At fair value through OCI
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	2	2
At fair value through OCI | Trade payables and fixed assets payables
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	0	0
At fair value through OCI | Borrowings
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	0	0
At fair value through OCI | Other financial liabilities
Disclosure of detailed information about financial instruments [line items]
Financial liabilities	2	2
Cash and cash equivalents
Disclosure of detailed information about financial instruments [line items]
Financial assets	290	439
Trade receivables
Disclosure of detailed information about financial instruments [line items]
Financial assets	586	341
Other financial assets
Disclosure of detailed information about financial instruments [line items]
Financial assets	79	57
At amortized cost
Disclosure of detailed information about financial instruments [line items]
Financial assets	290	442
At amortized cost | Cash and cash equivalents
Disclosure of detailed information about financial instruments [line items]
Financial assets	290	439
At amortized cost | Trade receivables
Disclosure of detailed information about financial instruments [line items]
Financial assets	0	0
At amortized cost | Other financial assets
Disclosure of detailed information about financial instruments [line items]
Financial assets	0	3
At fair value through profit and loss
Disclosure of detailed information about financial instruments [line items]
Financial assets	73	40
At fair value through profit and loss | Cash and cash equivalents
Disclosure of detailed information about financial instruments [line items]
Financial assets	0	0
At fair value through profit and loss | Trade receivables
Disclosure of detailed information about financial instruments [line items]
Financial assets	0	0
At fair value through profit and loss | Other financial assets
Disclosure of detailed information about financial instruments [line items]
Financial assets	73	40
At fair value through OCI
Disclosure of detailed information about financial instruments [line items]
Financial assets	592	355
At fair value through OCI | Cash and cash equivalents
Disclosure of detailed information about financial instruments [line items]
Financial assets	0	0
At fair value through OCI | Trade receivables
Disclosure of detailed information about financial instruments [line items]
Financial assets	586	341
At fair value through OCI | Other financial assets
Disclosure of detailed information about financial instruments [line items]
Financial assets	€ 6	€ 14

FINANCIAL INSTRUMENTS - Other F

FINANCIAL INSTRUMENTS - Other Financial Assets and Other Financial Liabilities Positions (Details) - EUR (€)	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Disclosure of detailed information about financial instruments [line items]
Non-current derivatives assets	€ 16,000,000		€ 18,000,000
Current derivatives assets	63,000,000		39,000,000
Derivative financial assets	79,000,000		57,000,000
Non-current derivatives liabilities	10,000,000		41,000,000
Current derivative liabilities	26,000,000		46,000,000
Derivatives liabilities	36,000,000		87,000,000
Payment for forward purchase currency bought-out before maturity	(29,000,000)	€ 2,000,000
Aluminium and premium future contracts
Disclosure of detailed information about financial instruments [line items]
Non-current derivatives liabilities	1,000,000		3,000,000
Current derivative liabilities	7,000,000		6,000,000
Derivatives liabilities	8,000,000		9,000,000
Other future contracts
Disclosure of detailed information about financial instruments [line items]
Non-current derivatives liabilities	0		0
Current derivative liabilities	1,000,000		1,000,000
Derivatives liabilities	1,000,000		1,000,000
Currency commercial contracts
Disclosure of detailed information about financial instruments [line items]
Non-current derivatives liabilities	2,000,000		4,000,000
Current derivative liabilities	16,000,000		28,000,000
Derivatives liabilities	18,000,000		32,000,000
Currency net debt derivatives
Disclosure of detailed information about financial instruments [line items]
Non-current derivatives liabilities	7,000,000		34,000,000
Current derivative liabilities	2,000,000		11,000,000
Derivatives liabilities	9,000,000		45,000,000
Currency net debt derivatives | Forward purchase contracts versus EURO
Disclosure of detailed information about financial instruments [line items]
Forward purchase currency bought-out before maturity	325,000,000
Payment for forward purchase currency bought-out before maturity	27,000,000
Aluminium and premium future contracts
Disclosure of detailed information about financial instruments [line items]
Non-current derivatives assets	8,000,000		1,000,000
Current derivatives assets	42,000,000		18,000,000
Derivative financial assets	50,000,000		19,000,000
Energy future contracts
Disclosure of detailed information about financial instruments [line items]
Non-current derivatives assets	0		0
Current derivatives assets	1,000,000		0
Derivative financial assets	1,000,000		0
Other future contracts
Disclosure of detailed information about financial instruments [line items]
Non-current derivatives assets	1,000,000		1,000,000
Current derivatives assets	3,000,000		1,000,000
Derivative financial assets	4,000,000		2,000,000
Currency commercial contracts
Disclosure of detailed information about financial instruments [line items]
Non-current derivatives assets	7,000,000		16,000,000
Current derivatives assets	17,000,000		17,000,000
Derivative financial assets	24,000,000		33,000,000
Margin call
Disclosure of detailed information about financial instruments [line items]
Non-current derivatives assets	0		0
Current derivatives assets	0		3,000,000
Derivative financial assets	€ 0		€ 3,000,000

FINANCIAL INSTRUMENTS - Narrati

FINANCIAL INSTRUMENTS - Narrative (Details) - Fair value - Level 1 € in Millions	Jun. 30, 2021EUR (€)
Constellium SE Senior Notes Due 2024
Disclosure of detailed information about financial instruments [line items]
Percentage of fair value senior notes issued	102.00%
Senior notes issued	€ 839
Constellium SE Senior Unsecured Notes Ddue 2025
Disclosure of detailed information about financial instruments [line items]
Percentage of fair value senior notes issued	108.00%
Senior notes issued	€ 294
Constellium SE Senior Notes Due 2026
Disclosure of detailed information about financial instruments [line items]
Percentage of fair value senior notes issued	99.00%
Senior notes issued	€ 418
Constellium SE Senir Notes Due 2028
Disclosure of detailed information about financial instruments [line items]
Percentage of fair value senior notes issued	100.00%
Senior notes issued	€ 299

FINANCIAL INSTRUMENTS - Derivat

FINANCIAL INSTRUMENTS - Derivatives Measured at Fair Value (Details) - EUR (€) € in Millions	Jun. 30, 2021	Dec. 31, 2020
Disclosure of financial instruments measured at fair value [line items]
Other financial assets - derivatives	€ 79	€ 57
Other financial liabilities - derivatives	36	87
Level 1
Disclosure of financial instruments measured at fair value [line items]
Other financial assets - derivatives	44	20
Other financial liabilities - derivatives	8	9
Level 2
Disclosure of financial instruments measured at fair value [line items]
Other financial assets - derivatives	35	37
Other financial liabilities - derivatives	28	78
Level 3
Disclosure of financial instruments measured at fair value [line items]
Other financial assets - derivatives	0	0
Other financial liabilities - derivatives	€ 0	€ 0

FINANCIAL RISK MANAGEMENT - Nar

FINANCIAL RISK MANAGEMENT - Narrative (Details) $ in Millions	Jun. 30, 2021EUR (€)	Jun. 30, 2021USD ($)	Dec. 31, 2020EUR (€)	Dec. 31, 2020USD ($)	Jun. 30, 2020EUR (€)	Dec. 31, 2019EUR (€)
Disclosure of liquidity risk [line items]
Margin requirement	€ 63,000,000		€ 39,000,000
Revolving credit facilities outstanding availability	461,000,000
Liquidity value	887,000,000
Cash and cash equivalents	290,000,000		439,000,000		€ 378,000,000	€ 184,000,000
Undrawn facilities	597,000,000
Margin call
Disclosure of liquidity risk [line items]
Margin requirement	€ 0		€ 3,000,000
Derivative classified as cash flow hedge
Disclosure of liquidity risk [line items]
Nominal amount hedging instrument | $		$ 305		$ 330
U.S. Revolving Facility
Disclosure of liquidity risk [line items]
Borrowing base | $		337
French Inventory Based Facility
Disclosure of liquidity risk [line items]
Borrowing base | $		82
German Facility
Disclosure of liquidity risk [line items]
Borrowing base | $		$ 50

FINANCIAL RISK MANAGEMENT - Eff

FINANCIAL RISK MANAGEMENT - Effect of Foreign Currency Derivatives Impacts and Commercial Transactions Exposures (Details) - EUR (€) € in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disclosure of nature and extent of risks arising from financial instruments [line items]
Realized (losses) / gains on foreign currency derivatives - net	€ (2)	€ (3)	€ (5)	€ (3)
Unrealized gains on foreign currency derivatives - net	3	0	11	(2)
Losses reclassified from OCI as a result of hedge accounting discontinuation	0	5	0	5
Derivatives that do not qualify for hedge accounting | At fair value through profit and loss
Disclosure of nature and extent of risks arising from financial instruments [line items]
Realized (losses) / gains on foreign currency derivatives - net	(2)	0	(4)	2
Unrealized gains on foreign currency derivatives - net	3	(1)	11	(2)
Derivatives that qualify for hedge accounting | At fair value through profit and loss
Disclosure of nature and extent of risks arising from financial instruments [line items]
Realized (losses) / gains on foreign currency derivatives - net	0	(3)	(1)	(5)
Unrealized gains on foreign currency derivatives - net	0	1	0	0
Losses reclassified from OCI as result of hedge accounting discontinuation	0	(5)	0	(5)
Losses reclassified from OCI as a result of hedge accounting discontinuation			5
Derivatives that qualify for hedge accounting | At fair value through OCI
Disclosure of nature and extent of risks arising from financial instruments [line items]
Unrealized gains on foreign currency derivatives - net	2	2	(9)	(6)
Gains / (losses) reclassified from cash flow hedge reserve to the Interim Income Statement	€ 1	€ 3	€ 1	€ 6

PENSIONS AND OTHER POST-EMPLO_3

PENSIONS AND OTHER POST-EMPLOYMENT BENEFIT OBLIGATIONS - Actuarial Assumptions (Details)	Jun. 30, 2021	Dec. 31, 2020
Switzerland
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Discount rate	0.20%	0.00%
U.S.
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Discount rate	0.00%	0.00%
U.S. | Hourly pension | Bottom of range
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Discount rate	2.75%	2.45%
U.S. | Hourly pension | Top of range
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Discount rate	2.95%	2.65%
U.S. | Salaried pension
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Discount rate	2.85%	2.55%
U.S. | OPEB | Bottom of range
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Discount rate	2.85%	2.50%
U.S. | OPEB | Top of range
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Discount rate	3.15%	2.80%
U.S. | Other benefits | Bottom of range
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Discount rate	2.50%	2.20%
U.S. | Other benefits | Top of range
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Discount rate	2.90%	2.55%
France
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Discount rate	0.00%	0.00%
France | Retirements
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Discount rate	0.90%	0.50%
France | Other benefits
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Discount rate	0.75%	0.40%
Germany
Disclosure of sensitivity analysis for actuarial assumptions [line items]
Discount rate	0.95%	0.55%

PENSIONS AND OTHER POST-EMPLO_4

PENSIONS AND OTHER POST-EMPLOYMENT BENEFIT OBLIGATIONS - Amounts Recognized in the Consolidated Statement of Financial Position (Details) - EUR (€) € in Millions	Jun. 30, 2021	Dec. 31, 2020
Disclosure of net defined benefit liability (asset) [line items]
Present value of funded obligation	€ 741	€ 772
Fair value of plan assets	(504)	(458)
Deficit of funded plans	237	314
Present value of unfunded obligation	344	350
Net liability arising from defined benefit obligation	581	664
Pension Benefits
Disclosure of net defined benefit liability (asset) [line items]
Present value of funded obligation	741	772
Fair value of plan assets	(504)	(458)
Deficit of funded plans	237	314
Present value of unfunded obligation	131	134
Net liability arising from defined benefit obligation	368	448
Other Benefits
Disclosure of net defined benefit liability (asset) [line items]
Present value of funded obligation	0	0
Fair value of plan assets	0	0
Deficit of funded plans	0	0
Present value of unfunded obligation	213	216
Net liability arising from defined benefit obligation	€ 213	€ 216

PENSIONS AND OTHER POST-EMPLO_5

PENSIONS AND OTHER POST-EMPLOYMENT BENEFIT OBLIGATIONS - Amounts Recognized in the Consolidated Income Statement (Details) - EUR (€) € in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of defined benefit plans [line items]
Current service cost	€ (8)	€ (6)	€ (15)	€ (14)
Past service cost	(2)	(2)	(2)	(2)
Net interest	(2)	(3)	(4)	(6)
Immediate recognition of gains arising over the year	0	(1)	1	0
Administration expenses	0	(1)	(1)	(1)
Total	(12)	(13)	(21)	(23)
Pension Benefits
Disclosure of defined benefit plans [line items]
Current service cost	(6)	(5)	(11)	(11)
Past service cost	0	0	0	0
Net interest	(1)	(2)	(2)	(3)
Immediate recognition of gains arising over the year	0	0	0	0
Administration expenses	0	(1)	(1)	(1)
Total	(7)	(8)	(14)	(15)
Other Benefits
Disclosure of defined benefit plans [line items]
Current service cost	(2)	(1)	(4)	(3)
Past service cost	(2)	(2)	(2)	(2)	€ (2)	€ (3)	€ 36
Net interest	(1)	(1)	(2)	(3)
Immediate recognition of gains arising over the year	0	(1)	1	0
Administration expenses	0	0	0	0
Total	€ (5)	€ (5)	€ (7)	€ (8)

PENSIONS AND OTHER POST-EMPLO_6

PENSIONS AND OTHER POST-EMPLOYMENT BENEFIT OBLIGATIONS - Movement in Net Defined Benefit Obligations (Details) € in Millions, $ in Millions	3 Months Ended		6 Months Ended			12 Months Ended
	Jun. 30, 2021EUR (€)	Jun. 30, 2020EUR (€)	Jun. 30, 2021EUR (€)	Jun. 30, 2021USD ($)	Jun. 30, 2020EUR (€)	Dec. 31, 2020EUR (€)	Dec. 31, 2019EUR (€)	Dec. 31, 2018EUR (€)
Disclosure of net defined benefit liability (asset) [line items]
At January 1, 2021			€ 664	$ 664
Current service cost	€ 8	€ 6	15		€ 14
Interest cost / (income)	2	3	4		6
Past service cost	2	2	2		2
Immediate recognition of gains arising over the year	0	1	(1)		0
Administration expenses	0	1	1		1
Remeasurements due to:
—actual return less interest on plan assets			(43)
—changes in financial assumptions			(48)
—changes in demographic assumptions			0
—experience losses			0
Effects of changes in foreign exchange rates			8
Benefits paid			(11)
Contributions by the Group			(10)
Contributions by the plan participants			0
At June 30, 2021	581		581			€ 664
Pension Benefits
Disclosure of net defined benefit liability (asset) [line items]
Current service cost	6	5	11		11
Interest cost / (income)	1	2	2		3
Past service cost	0	0	0		0
Immediate recognition of gains arising over the year	0	0	0		0
Administration expenses	0	1	1		1
Other Benefits
Disclosure of net defined benefit liability (asset) [line items]
Current service cost	2	1	4		3
Interest cost / (income)	1	1	2		3
Past service cost	2	2	2		2	2	€ 3	€ (36)
Immediate recognition of gains arising over the year	0	1	(1)		0
Administration expenses	0	€ 0	0		€ 0
Defined benefit obligations
Disclosure of net defined benefit liability (asset) [line items]
At January 1, 2021			1,122
Current service cost			15
Interest cost / (income)			7
Past service cost			2
Immediate recognition of gains arising over the year			(1)
Administration expenses			0
Remeasurements due to:
—actual return less interest on plan assets			0
—changes in financial assumptions			(48)
—changes in demographic assumptions			0
—experience losses			0
Effects of changes in foreign exchange rates			11
Benefits paid			(26)
Contributions by the Group			0
Contributions by the plan participants			3
At June 30, 2021	1,085		1,085			1,122
Defined benefit obligations | Pension Benefits
Disclosure of net defined benefit liability (asset) [line items]
At January 1, 2021			906
Current service cost			11
Interest cost / (income)			5
Past service cost			0
Immediate recognition of gains arising over the year			0
Administration expenses			0
Remeasurements due to:
—actual return less interest on plan assets			0
—changes in financial assumptions			(39)
—changes in demographic assumptions			0
—experience losses			(1)
Effects of changes in foreign exchange rates			5
Benefits paid			(17)
Contributions by the Group			0
Contributions by the plan participants			2
At June 30, 2021	872		872			906
Defined benefit obligations | Other Benefits
Disclosure of net defined benefit liability (asset) [line items]
At January 1, 2021			216
Current service cost			4
Interest cost / (income)			2
Past service cost			2
Immediate recognition of gains arising over the year			(1)
Administration expenses			0
Remeasurements due to:
—actual return less interest on plan assets			0
—changes in financial assumptions			(9)
—changes in demographic assumptions			0
—experience losses			1
Effects of changes in foreign exchange rates			6
Benefits paid			(9)
Contributions by the Group			0
Contributions by the plan participants			1
At June 30, 2021	213		213			216
Plan Assets
Disclosure of net defined benefit liability (asset) [line items]
At January 1, 2021			(458)
Current service cost			0
Interest cost / (income)			(3)
Past service cost			0
Immediate recognition of gains arising over the year			0
Administration expenses			1
Remeasurements due to:
—actual return less interest on plan assets			(43)
—changes in financial assumptions			0
—changes in demographic assumptions			0
—experience losses			0
Effects of changes in foreign exchange rates			(3)
Benefits paid			15
Contributions by the Group			(10)
Contributions by the plan participants			(3)
At June 30, 2021	€ (504)		€ (504)			€ (458)

PENSIONS AND OTHER POST-EMPLO_7

PENSIONS AND OTHER POST-EMPLOYMENT BENEFIT OBLIGATIONS - Narrative (Details) - EUR (€) € in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of defined benefit plans [line items]
Gain (loss) recognized due to change in benefits	€ 2	€ 2	€ 2	€ 2
Other Benefits
Disclosure of defined benefit plans [line items]
Gain (loss) recognized due to change in benefits	€ 2	€ 2	€ 2	€ 2	€ 2	€ 3	€ (36)

PENSIONS AND OTHER POST-EMPLO_8

PENSIONS AND OTHER POST-EMPLOYMENT BENEFIT OBLIGATIONS - Net Defined Benefit Obligations by Country (Details) € in Millions, $ in Millions	Jun. 30, 2021EUR (€)	Dec. 31, 2020EUR (€)	Dec. 31, 2020USD ($)
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligations	€ 1,085	€ 1,122
Plan assets	(504)	(458)
Net defined benefit liability	581	664	$ 664
France
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligations	163	168
Plan assets	(5)	(5)
Net defined benefit liability	158	163
Germany
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligations	134	143
Plan assets	(2)	(1)
Net defined benefit liability	132	142
Switzerland
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligations	295	310
Plan assets	(248)	(223)
Net defined benefit liability	47	87
United States
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligations	492	500
Plan assets	(249)	(229)
Net defined benefit liability	243	271
Other
Disclosure of net defined benefit liability (asset) [line items]
Defined benefit obligations	1	1
Plan assets	0	0
Net defined benefit liability	€ 1	€ 1

PROVISIONS - Changes in Provisi

PROVISIONS - Changes in Provisions (Details) - EUR (€) € in Millions	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Changes in other provisions [abstract]
At January 1, 2021	€ 121
Allowance	4
Amounts used	(5)
Unused amounts reversed	(4)
Unwinding of discounts	(2)
Effects of changes in foreign exchange rates	1
At June 30, 2021	115
Current	20	€ 23
Non-Current	95	98
Total Provisions	115	121
Close down and environmental remediation costs
Changes in other provisions [abstract]
At January 1, 2021	88
Allowance	0
Amounts used	0
Unused amounts reversed	0
Unwinding of discounts	(2)
Effects of changes in foreign exchange rates	1
At June 30, 2021	87
Current	7
Non-Current	80
Total Provisions	87	88
Restructuring costs
Changes in other provisions [abstract]
At January 1, 2021	6
Allowance	3
Amounts used	(3)
Unused amounts reversed	(1)
Unwinding of discounts	0
Effects of changes in foreign exchange rates	0
At June 30, 2021	5
Current	3
Non-Current	2
Total Provisions	5	6
Legal claims and other costs
Changes in other provisions [abstract]
At January 1, 2021	27
Allowance	1
Amounts used	(2)
Unused amounts reversed	(3)
Unwinding of discounts	0
Effects of changes in foreign exchange rates	0
At June 30, 2021	23
Current	10
Non-Current	13
Total Provisions	€ 23	€ 27

PROVISIONS - Legal Claims and O

PROVISIONS - Legal Claims and Other Costs (Details) - Legal claims and other costs - EUR (€) € in Millions	Jun. 30, 2021	Dec. 31, 2020
Disclosure of other provisions [line items]
Litigation	€ 17	€ 21
Disease claims	5	5
Other	1	1
Total Provisions for legal claims and other costs	€ 23	€ 27

NON-CASH INVESTING AND FINANC_2

NON-CASH INVESTING AND FINANCING TRANSACTIONS (Details) - EUR (€) € in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Disclosure of cash flow statement [Abstract]
Property, plant and equipment acquired by finance lease	€ 8	€ 25
Fair value of vested PSUs and RSUs	€ 15	€ 0

SHARE CAPITAL - Narrative (Deta

SHARE CAPITAL - Narrative (Details)	3 Months Ended	6 Months Ended
	Jun. 30, 2020shares	Jun. 30, 2020shares	Jun. 30, 2021EUR (€)€ / sharesshares	Dec. 31, 2020EUR (€)shares
Disclosure of classes of share capital [line items]
Share capital | €			€ 2,833,547.32	€ 3,000,000
Nominal value of ordinary fully-paid shares (in EUR per share) | € / shares			€ 0.02
Number of vote rights per share			1
Antidilutive securities (in shares)	4,880,758	4,878,787
Ordinary shares
Disclosure of classes of share capital [line items]
Number of ordinary shares (in shares)			141,677,366	139,962,672

SHARE CAPITAL (Details)

SHARE CAPITAL (Details) € in Millions	6 Months Ended
	Jun. 30, 2021EUR (€)shares
Disclosure of classes of share capital [line items]
Beginning balance	€ (101)
Ending balance	144
Share capital
Disclosure of classes of share capital [line items]
Beginning balance	3
New shares issued	0
Ending balance	3
Share premium
Disclosure of classes of share capital [line items]
Beginning balance	420
New shares issued	0
Ending balance	€ 420
Ordinary shares
Disclosure of classes of share capital [line items]
Beginning balance (in shares) | shares	139,962,672
Ending balance (in shares) | shares	141,677,366
Ordinary shares | Employees
Disclosure of classes of share capital [line items]
New shares issued (in shares) | shares	1,714,694

SHARE-BASED COMPENSATION - Narr

SHARE-BASED COMPENSATION - Narrative (Details) € / shares in Units, € in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2020shares	Jun. 30, 2021EUR (€)shares€ / shares	Jun. 30, 2020EUR (€)shares	Jun. 30, 2018
Share Based Payment Plans [line items]
Potential additional shares granted (in shares)		1,149,054
Expense from share-based payment transactions with employees | €		€ 7	€ 8
Antidilutive securities (in shares)	4,880,758		4,878,787
PSUs
Share Based Payment Plans [line items]
Share based compensation, vesting period		3 years
Fair value at grant date (in euros) (in EUR per share) | € / shares		€ 21.84
PSUs | Bottom of range
Share Based Payment Plans [line items]
Percentage of vesting multiplier		0.00%
PSUs | Top of range
Share Based Payment Plans [line items]
Percentage of vesting multiplier		200.00%
PSUs granted in May 2018
Share Based Payment Plans [line items]
Total shareholder return (TSR) percentage achieved				182.90%
PSUs vested in May 2021
Share Based Payment Plans [line items]
Potential additional shares granted (in shares)		1,161,718
RSUs
Share Based Payment Plans [line items]
Potential additional shares granted (in shares)		534,499
Vesting period on the grant date		3 years
Fair value at grant date (in euros) (in EUR per share) | € / shares		€ 13.9

SHARE-BASED COMPENSATION - Inpu

SHARE-BASED COMPENSATION - Inputs to the Model Used for PSUs Granted (Details) - PSUs	6 Months Ended
	Jun. 30, 2021€ / shares
Disclosure of Input of Model Used for Performance-Based RSU [Line Items]
Fair value at grant date (in euros) (in EUR per share)	€ 21.84
Share price at grant date (in EUR per share)	€ 13.90
Dividend yield	0.00%
Expected volatility	71.00%
Risk-free interest rate (US government bond yield)	0.31%

SHARE-BASED COMPENSATION - Numb

SHARE-BASED COMPENSATION - Number and Movement of Potential Shares (Details)	6 Months Ended
	Jun. 30, 2021shares
Disclosure of movement of potential shares [line items]
Potential Shares, Beginning balance (in shares)	4,859,150
Potential Shares, Granted (in shares)	1,149,054
Potential Shares, Over-performance (in shares)	526,551
Potential Shares, Vested (in shares)	(1,714,694)
Potential Shares, Forfeited (in shares)	(40,785)
Potential Shares, Ending balance (in shares)	4,779,276
Performance-Based RSU
Disclosure of movement of potential shares [line items]
Potential Shares, Beginning balance (in shares)	2,594,327
Potential Shares, Granted (in shares)	614,555
Potential Shares, Over-performance (in shares)	526,551
Potential Shares, Vested (in shares)	(1,161,718)
Potential Shares, Forfeited (in shares)	(9,970)
Potential Shares, Ending balance (in shares)	2,563,745
Percentage of vesting multiplier	100.00%
Performance based shares forfeited upon departure of certain beneficiaries (in shares)	9,970
Performance based shares forfeited upon non-fulfillment of performance conditions (in shares)	0
Restricted Stock Units
Disclosure of movement of potential shares [line items]
Potential Shares, Beginning balance (in shares)	2,231,911
Potential Shares, Granted (in shares)	534,499
Potential Shares, Over-performance (in shares)	0
Potential Shares, Vested (in shares)	(520,064)
Potential Shares, Forfeited (in shares)	(30,815)
Potential Shares, Ending balance (in shares)	2,215,531
Equity Award Plans
Disclosure of movement of potential shares [line items]
Potential Shares, Beginning balance (in shares)	32,912
Potential Shares, Granted (in shares)	0
Potential Shares, Over-performance (in shares)	0
Potential Shares, Vested (in shares)	(32,912)
Potential Shares, Forfeited (in shares)	0
Potential Shares, Ending balance (in shares)	0

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details)	Jul. 29, 2021EUR (€)credit_facility	Jun. 30, 2021EUR (€)	Dec. 31, 2020EUR (€)	Dec. 31, 2019EUR (€)
Disclosure of non-adjusting events after reporting period [line items]
Amount drawn under credit facility		€ 2,257,000,000	€ 2,391,000,000	€ 2,361,000,000
Expiration of Credit Facilities | Secured and Unsecured German Credit Facilities due 2022 | German State
Disclosure of non-adjusting events after reporting period [line items]
Number of credit facilities | credit_facility	2
Amount drawn under credit facility	€ 0