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General Information - Consolidated Subsidiaries Acquired or Newly Established (Detail) | 12 Months Ended
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Dec. 31, 2025 | Dec. 31, 2024
Disclosure of subsidiaries [line items] |  |  |
Ownership (%) | [1] | 43.00% | 43.00%
Total for all subsidiaries [member] | POSCO DEEPTECH IP FUND [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-06 |
Ownership (%) |  | 60.00% |
Reason |  | New establishment |
Total for all subsidiaries [member] | FUTURE GRAPH CO., LTD. P&O Chemical Co., Ltd [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-06 |
Ownership (%) |  | 100.00% |
Reason |  | New establishment |
Total for all subsidiaries [member] | CHEMGAS KOREA CO.,LTD. |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-07 |
Ownership (%) |  | 100.00% |
Reason |  | Acquisition |
Total for all subsidiaries [member] | POSCO-EVER NEW MEDICAL Investment Fund [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-07 |
Ownership (%) |  | 60.00% |
Reason |  | New establishment |
Total for all subsidiaries [member] | POSCO Stainless Precision & Processing [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-08 |
Ownership (%) |  | 100.00% |
Reason |  | New establishment |
Total for all subsidiaries [member] | POSCO INTERNATIONAL CVC 1st Fund [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-08 |
Ownership (%) |  | 100.00% |
Reason |  | New establishment |
Total for all subsidiaries [member] | POSCO CVC 1st Fund [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-08 |
Ownership (%) |  | 100.00% |
Reason |  | New establishment |
Total for all subsidiaries [member] | New Zero 2nd Co., Ltd. [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-09 |
Ownership (%) |  | 100.00% |
Reason |  | Acquisition |
Total for all subsidiaries [member] | POSCO DX CVC 1st Fund [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-09 |
Ownership (%) |  | 100.00% |
Reason |  | New establishment |
Total for all subsidiaries [member] | POSCO Group AC Fund I [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-09 |
Ownership (%) |  | 100.00% |
Reason |  | New establishment |
Total for all subsidiaries [member] | POSCO Safety Solution [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-09 |
Ownership (%) |  | 100.00% |
Reason |  | New establishment |
Total for all subsidiaries [member] | Startup Korea Posco group Openinnovation Fund [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-11 |
Ownership (%) |  | 70.00% |
Reason |  | New establishment |
Total for all subsidiaries [member] | POSCO INTERNATIONAL ALASKA ENERGY LLC [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-11 |
Ownership (%) |  | 100.00% |
Reason |  | New establishment |
Total for all subsidiaries [member] | FLOW K CO., Ltd. [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-11 |
Ownership (%) |  | 70.00% |
Reason |  | Transfer from associate to subsidiary |
Total for all subsidiaries [member] | POSCO FLOW VIETNAM CO LTD [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-12 |
Ownership (%) |  | 100.00% |
Reason |  | New establishment |
Total for all subsidiaries [member] | PT Prime Agri Resources [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-12 |
Ownership (%) |  | 65.72% |
Reason |  | Acquisition |
Total for all subsidiaries [member] | SANPU TRADING Co., Ltd. [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-05 |
Reason |  | Liquidation |
Total for all subsidiaries [member] | New Energy Hub [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-06 |
Reason |  | Merger |
Total for all subsidiaries [member] | POSCO CNGR Nickel Solution [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-07 |
Reason |  | Liquidation |
Total for all subsidiaries [member] | POSCO E&C Vietnam Co., Ltd. [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-08 |
Reason |  | Divestiture |
Total for all subsidiaries [member] | SK SOLRA POWER GENERATION COPORATION [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-08 |
Reason |  | Divestiture |
Total for all subsidiaries [member] | POSCO (Suzhou) Steel Processing Center CO., LTD [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-10 |
Reason |  | Liquidation |
Total for all subsidiaries [member] | SUZHOU POSCO-CORE TECHNOLOGY CO., LTD [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-12 |
Reason |  | Divestiture |
Total for all subsidiaries [member] | Mastern No.123 Yeoju Samgyo PFV CO., Ltd [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-12 |
Reason |  | Divestiture |
Total for all subsidiaries [member] | POSCO ENGINEERING & CONSTRUCTION DO BRAZIL LTDA. [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-12 |
Reason |  | Liquidation |
Total for all subsidiaries [member] | Consus Private Real Estate Fund 2 [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-12 |
Reason |  | Liquidation |
Total for all subsidiaries [member] | Consus Pf Private Real Estate Fund No.2 [Member] |  |  |
Disclosure of subsidiaries [line items] |  |  |
Date of addition |  | 2025-12 |
Reason |  | Liquidation |
[1] | As of December 31, 2025, the entities are classified as consolidated subsidiaries since the Company has control over the investees although the Company’s percentage of ownership is 50% or less, considering the structure of the entities’ Board of Directors and others.

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