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v3.26.1

Related Party Transactions - Significant Transactions Between the Company, Excluding the Controlling Company, and Related Companies (Detail) - Company, excluding the controlling company [member] - KRW (₩) ₩ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
Disclosure of transactions between related parties [line items] |  |  |
Sales | ₩ 1,095,261 | ₩ 1,516,175 | ₩ 1,690,054
Dividends | 376,109 | 511,189 | 658,338
Other sales | 50,860 | 7,075 | 16,569
Purchase of material | 2,816,785 | 2,673,849 | 2,846,362
Other purchases | 52,815 | 266,115 | 115,979
New Songdo International City Development, LLC [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | 52,814 | 216,657 | 208,536
Other sales | 48,449 | 1,427 | 1,484
Other purchases | 54 | 145 | 279
SNNC [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | 101,468 | 121,658 | 164,827
Dividends |  |  | 0
Other sales | 8 | 8 | 87
Purchase of material | 484,571 | 377,168 | 637,638
Other purchases | 4,163 | 3,620 | 1,749
Noeul Green Energy Co., Ltd [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales |  |  | 6,499
Other sales |  |  | 28
Other purchases |  |  | 10,320
POS-SEAH STEEL WIRE (TIANJIN) CO., Ltd |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | 13,185 | 13,733 | 14,477
POS SeAH Steel Wire(Nantong) Co., Ltd. |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | 51,513 | 52,993 | 43,811
Purchase of material | 357 | 243 | 73
South-East Asia Gas Pipeline Company Ltd. [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Dividends | 37,273 | 64,208 | 59,295
Other sales |  |  | 0
POSCO MC MATERIALS [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | 132,097 | 137,209 | 113,542
Dividends | 3,000 | 1,800 | 9,000
Purchase of material | 6,913 | 8,107 | 6,861
Other purchases | 820 | 526 | 1,564
Samcheok blue power co., ltd. [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | 246,619 | 377,636 | 503,283
Dividends | 2,795 | 10,993 | 10,020
Other sales | 352 | 946 | 0
Purchase of material | 20 |  |
Other purchases | 4 |  |
Pocheon-Hwado Highway Corp. [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales |  | 59,691 | 160,233
Other purchases |  | 65 |
Roy Hill Holdings Pty Ltd [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Dividends | 213,794 | 284,541 | 367,445
Other sales | 0 | 260 |
Purchase of material | 1,544,120 | 1,729,832 | 1,611,073
Other associates and joint ventures [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | 224,899 | 421,095 | 474,846
Dividends | 119,247 | 149,647 | 212,578
Other sales | 2,051 | 4,434 | 14,970
Purchase of material | 447,364 | 520,477 | 590,717
Other purchases | 42,945 | 255,084 | ₩ 102,067
HBIS-POSCO Automotive Steel Co., Ltd |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | 24,870 | 41,369 |
Purchase of material | 66,886 | 37,241 |
Other purchases | 1,391 |  |
POSCO-SAMSUNG-SLOVAKIA PROCESSING CENTER |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | 44,882 | 43,098 |
Purchase of material | 5 | 781 |
POSCO(Guangdong) Automotive Steel Co, Ltd [member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | 195,811 |  |
Purchase of material | 266,549 |  |
Gyeonggi Green Energy Co., Ltd. [Member] |  |  |
Disclosure of transactions between related parties [line items] |  |  |
Sales | 7,103 | 31,036 |
Other purchases | ₩ 3,438 | ₩ 6,675 |

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