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General Information - Details of Joint Ventures (Detail) | 12 Months Ended
--- | ---
Dec. 31, 2025 | Dec. 31, 2024
Disclosure of joint ventures [line items] |  |  |
Category of business | [1] | Steel manufacturing and sales |
Domestic [member] | POSCO MC MATERIALS [Member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Steel processing and sales |
Ownership (%) |  | 60.00% | 60.00%
Region |  | Gwangyang |
Domestic [member] | SNNC [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Raw material manufacturing and sales |
Ownership (%) |  | 49.00% | 49.00%
Region |  | Gwangyang |
Domestic [member] | POSCO-KB Shipbuilding Restructuring Fund [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Investment in new technologies |
Ownership (%) |  | 18.75% | 18.75%
Region |  | Seoul |
Domestic [member] | POSCO-NSC Venture Fund [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Investment in new technologies |
Ownership (%) |  | 16.67% | 16.67%
Region |  | Seoul |
Domestic [member] | PoscoPlutus Project 3rd Project fund [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Investment in new technologies |
Ownership (%) |  | 5.96% | 5.96%
Region |  | Seoul |
Domestic [member] | PCC Bio 2nd Fund [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Investment in new technologies |
Ownership (%) |  | 19.72% | 19.72%
Region |  | Seoul |
Domestic [member] | Union PCC Portfolio Fund [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Investment in new technologies |
Ownership (%) |  | 14.12% | 14.12%
Region |  | Seoul |
Domestic [member] | Eco Energy Solution Co., ltd [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Service |
Ownership (%) |  | 50.00% | 50.00%
Region |  | Seoul |
Domestic [member] | FLOW K CO., Ltd. [Member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Logistics and warehousing |
Ownership (%) |  | 0.00% | 40.00%
Region |  | — |
Foreign [member] | KOBRASCO [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Steel materials manufacturing and sales |
Ownership (%) |  | 50.00% | 50.00%
Region |  | Brazil |
Foreign [member] | BX STEEL POSCO Cold Rolled Sheet Co., Ltd. [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Steel processing and sales |
Ownership (%) |  | 25.00% | 25.00%
Region |  | China |
Foreign [member] | POSCO-SAMSUNG-Slovakia Processing Center [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Steel processing and sales |
Ownership (%) |  | 30.00% | 30.00%
Region |  | Slovakia |
Foreign [member] | YULCHON MEXICO S.A. DE C.V. [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Tube for automobile manufacturing |
Ownership (%) |  | 11.85% | 11.85%
Region |  | Mexico |
Foreign [member] | Hyunson Engineering & Construction HYENCO [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Construction |
Ownership (%) |  | 4.89% | 4.89%
Region |  | Algeria |
Foreign [member] | POSCO E&C Saudi Arabia [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Civil engineering and construction |
Ownership (%) |  | 40.00% | 40.00%
Region |  | Saudi Arabia |
Foreign [member] | Pos-Austem Suzhou Automotive Co., Ltd [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Automotive parts manufacturing |
Ownership (%) |  | 19.90% | 19.90%
Region |  | China |
Foreign [member] | POS-InfraAuto (Suzhou) Co., Ltd [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Automotive parts manufacturing |
Ownership (%) |  | 16.20% | 16.20%
Region |  | China |
Foreign [member] | POS-AUSTEM YANTAI AUTOMOTIVE CO.,LTD [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Automotive parts manufacturing |
Ownership (%) |  | 11.10% | 11.10%
Region |  | China |
Foreign [member] | POS-AUSTEM WUHAN AUTOMOTIVE CO., LTD [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Automotive parts manufacturing |
Ownership (%) |  | 7.43% | 7.43%
Region |  | China |
Foreign [member] | DMSA/AMSA [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Energy & resource development |
Ownership (%) |  | 3.89% | 3.89%
Region |  | Madagascar |
Foreign [member] | Roy Hill Holdings Pty Ltd. [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Energy & resource development |
Ownership (%) |  | 12.50% | 12.50%
Region |  | Australia |
Foreign [member] | POSCO-NPS Niobium LLC [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Mine development |
Ownership (%) |  | 50.00% | 50.00%
Region |  | USA |
Foreign [member] | HBIS-POSCO Automotive Steel Co., Ltd [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Steel manufacturing and sales |
Ownership (%) |  | 50.00% | 50.00%
Region |  | China |
Foreign [member] | PT NICOLE METAL INDUSTRY [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Nickel smelting |
Ownership (%) |  | 49.00% | 49.00%
Region |  | Indonesia |
Foreign [member] | Hydrogen Duqm LLC [Member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Green hydrogen/Ammonia product business development |
Ownership (%) |  | 44.80% | 44.80%
Region |  | Oman |
Foreign [member] | Nickel Mining Company SAS [member] |  |  |
Disclosure of joint ventures [line items] |  |  |
Category of business |  | Raw material manufacturing and sales |
Ownership (%) |  | 49.00% | 49.00%
Region |  | New Caledonia |
[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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