Borrowings - Short-term Borrowings and Current Portion of Long-term Borrowings (Detail) - KRW (₩) ₩ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024
Disclosure of detailed information about borrowings [line items]
Current borrowings and current portion of non-current borrowings	₩ 12,117,422	₩ 11,115,747
Short-term borrowings [member]
Disclosure of detailed information about borrowings [line items]
Short-term borrowings	7,431,957	5,733,091
Short-term borrowings [member] \| JP Morgan and others [member]
Disclosure of detailed information about borrowings [line items]
Short-term borrowings	137,852	85,892
Short-term borrowings [member] \| HSBC and others [member]
Disclosure of detailed information about borrowings [line items]
Short-term borrowings	7,294,105	5,647,199
Current portion of long-term liabilities [member]
Disclosure of detailed information about borrowings [line items]
Current portion of debentures	4,685,465	5,382,656
Current portion of long-term liabilities [member] \| Foreign currency exchangable bonds [member]
Disclosure of detailed information about borrowings [line items]
Current portion of debentures	₩ 44,509	39,053
Bottom of range [member] \| Short-term borrowings [member] \| JP Morgan and others [member]
Disclosure of detailed information about borrowings [line items]
Issuance date	January 2025
Maturity date	January 2026
Interest rate (%)	3.40%
Bottom of range [member] \| Short-term borrowings [member] \| HSBC and others [member]
Disclosure of detailed information about borrowings [line items]
Issuance date	January 2025
Maturity date	January 2026
Interest rate (%)	0.75%
Bottom of range [member] \| Current portion of long-term liabilities [member] \| Export-Import Bank of Korea and others [member]
Disclosure of detailed information about borrowings [line items]
Issuance date	December 2006
Maturity date	January 2026
Interest rate (%)	1.00%
Bottom of range [member] \| Current portion of long-term liabilities [member] \| KB Securities co.,Ltd. and others [Member]
Disclosure of detailed information about borrowings [line items]
Issuance date	July 2019
Maturity date	January 2026
Interest rate (%)	1.77%
Top of range [member] \| Short-term borrowings [member] \| JP Morgan and others [member]
Disclosure of detailed information about borrowings [line items]
Issuance date	December 2025
Maturity date	December 2026
Interest rate (%)	6.20%
Top of range [member] \| Short-term borrowings [member] \| HSBC and others [member]
Disclosure of detailed information about borrowings [line items]
Issuance date	December 2025
Maturity date	December 2026
Interest rate (%)	7.95%
Top of range [member] \| Current portion of long-term liabilities [member] \| Export-Import Bank of Korea and others [member]
Disclosure of detailed information about borrowings [line items]
Issuance date	December 2025
Maturity date	December 2026
Interest rate (%)	8.50%
Top of range [member] \| Current portion of long-term liabilities [member] \| KB Securities co.,Ltd. and others [Member]
Disclosure of detailed information about borrowings [line items]
Issuance date	September 2024
Maturity date	September 2026
Interest rate (%)	5.63%
Top of range [member] \| Current portion of long-term liabilities [member] \| Foreign currency exchangable bonds [member]
Disclosure of detailed information about borrowings [line items]
Issuance date	September 2021
Maturity date	September 2026
Gross amount [member] \| Current portion of long-term liabilities [member] \| Export-Import Bank of Korea and others [member]
Disclosure of detailed information about borrowings [line items]
Current portion of debentures	₩ 1,302,568	1,323,002
Gross amount [member] \| Current portion of long-term liabilities [member] \| KB Securities co.,Ltd. and others [Member]
Disclosure of detailed information about borrowings [line items]
Current portion of debentures	3,340,036	4,024,084
Discount on debentures [member] \| Current portion of long-term liabilities [member]
Disclosure of detailed information about borrowings [line items]
Current portion of debentures	₩ (1,648)	₩ (3,483)

The interest rate on borrowings. [Refer: Borrowings]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 7
-IssueDate 2025-01-01
-Paragraph 7
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2025-en-r&anchor=para_7&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_BorrowingsInterestRate
Namespace Prefix:	ifrs-full_
Data Type:	dtr-2022:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The maturity of borrowings. [Refer: Borrowings]

+ References

+ Details

Name:	ifrs-full_BorrowingsMaturity
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of current borrowings and current portion of non-current borrowings. [Refer: Borrowings]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 55
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_55&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_CurrentBorrowingsAndCurrentPortionOfNoncurrentBorrowings
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The current portion of non-current borrowings. [Refer: Borrowings]

+ References

+ Details

Name:	ifrs-full_CurrentPortionOfLongtermBorrowings
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	ifrs-full_DisclosureOfDetailedInformationAboutBorrowingsLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of current borrowings. [Refer: Borrowings]

+ References

+ Details

Name:	ifrs-full_ShorttermBorrowings
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Borrowings issuance date.

+ References

No definition available.

+ Details

Name:	pkx_BorrowingsIssuanceDate
Namespace Prefix:	pkx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Current portion of debentures.

+ References

No definition available.

+ Details

Name:	pkx_CurrentPortionOfDebenture
Namespace Prefix:	pkx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	ifrs-full_BorrowingsByNameAxis=ifrs-full_ShorttermBorrowingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CounterpartiesAxis=pkx_JPMorganMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CounterpartiesAxis=pkx_HSBCAndOthersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BorrowingsByNameAxis=pkx_CurrentPortionOfLongTermLiabilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CounterpartiesAxis=pkx_ForeignCurrencyExchangableBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_BottomOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CounterpartiesAxis=pkx_ExportImportBankOfKoreaAndOthersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CounterpartiesAxis=pkx_KbSecuritiesCoLtdAndOthersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis=ifrs-full_GrossCarryingAmountMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_CarryingAmountAccumulatedDepreciationAmortisationAndImpairmentAndGrossCarryingAmountAxis=pkx_DiscountOnDebenturesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: