Decrease in Fair Value of Financial Instrument

No definition available.

Name:	birk_DecreaseInFairValueOfFinancialInstrument
Namespace Prefix:	birk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Deferred offering costs.

+ References

No definition available.

+ Details

Name:	birk_DeferredOfferingCost
Namespace Prefix:	birk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Disclosure Of Detailed Information About Equity.

+ References

No definition available.

+ Details

Name:	birk_DisclosureOfDetailedInformationAboutEquityLineItems
Namespace Prefix:	birk_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Early repayment of borrowings

+ References

No definition available.

+ Details

Name:	birk_EarlyRepaymentOfBorrowings
Namespace Prefix:	birk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Initial public offering price per share

+ References

No definition available.

+ Details

Name:	birk_InitialPublicOfferingPricePerShare
Namespace Prefix:	birk_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares exercised, option to purchase additional shares.

+ References

No definition available.

+ Details

Name:	birk_NumberOfSharesExercisedOptionToPurchaseAdditionalShares
Namespace Prefix:	birk_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Ordinary share price.

+ References

No definition available.

+ Details

Name:	birk_OrdinarySharePrice
Namespace Prefix:	birk_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Shares repurchased amount of ordinary shares.

+ References

No definition available.

+ Details

Name:	birk_SharesRepurchasedAmountOfOrdinaryShares
Namespace Prefix:	birk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Shares repurchased of ordinary shares

+ References

No definition available.

+ Details

Name:	birk_SharesRepurchasedOfOrdinaryShares
Namespace Prefix:	birk_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Underwriting commission fees

+ References

No definition available.

+ Details

Name:	birk_UnderwritingCommissionFees1
Namespace Prefix:	birk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The exercise price of share options granted.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2025-01-01
-Paragraph 47
-Subparagraph a
-Clause i
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2025-en-r&anchor=para_47_a_i&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_ExercisePriceShareOptionsGranted2019
Namespace Prefix:	ifrs-full_
Data Type:	dtr-2022:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The explanation of the fact that shares have no par value. [Refer: Par value per share]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 160
-Subparagraph a
-Clause iii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_160_a_iii&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph B10
-Subparagraph a
-Clause iii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_B10_a_iii&doctype=Appendix&subtype=B
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 79
-Subparagraph a
-Clause iii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_79_a_iii&doctype=Standard
-URIDate 2025-03-27

+ Details

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

- Definition

The number of shares issued by the entity.

+ 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 106
-Subparagraph d
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_106_d&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_NumberOfSharesIssued
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of shares that have been authorised and issued, reduced by treasury shares held. [Refer: Treasury shares]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 160
-Subparagraph a
-Clause iv
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_160_a_iv&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph B10
-Subparagraph a
-Clause iv
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_B10_a_iv&doctype=Appendix&subtype=B
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 79
-Subparagraph a
-Clause iv
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_79_a_iv&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_NumberOfSharesOutstanding
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The nominal value per share.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph B10
-Subparagraph a
-Clause iii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_B10_a_iii&doctype=Appendix&subtype=B
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 160
-Subparagraph a
-Clause iii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_160_a_iii&doctype=Standard
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 79
-Subparagraph a
-Clause iii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_79_a_iii&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_ParValuePerShare
Namespace Prefix:	ifrs-full_
Data Type:	dtr-2022:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash inflow from issuing shares.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 7
-IssueDate 2025-01-01
-Paragraph 17
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=7&code=ifrs-tx-2025-en-r&anchor=para_17_a&doctype=Standard
-URIDate 2025-03-27

+ Details

Name:	ifrs-full_ProceedsFromIssuingShares
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

+ Details

Name:	ifrs-full_ShareIssueRelatedCost
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	ifrs-full_ClassesOfShareCapitalAxis=ifrs-full_OrdinarySharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_ClassesOfShareCapitalAxis=birk_OrdinarySharesSecondaryOfferingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_ClassesOfShareCapitalAxis=birk_AcceleratedShareRepurchaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_NonadjustingEventsAfterReportingPeriodAxis=birk_OrdinaryShareTransactionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=birk_BkLCLuxMidCoSARLMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_ComponentsOfEquityAxis=birk_InitialPublicOfferingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_ClassesOfFinancialInstrumentsAxis=birk_TermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Equity - Additional Information (Details) € / shares in Units, $ / shares in Units, € in Millions, $ in Millions									2 Months Ended	3 Months Ended	9 Months Ended		12 Months Ended
	May 21, 2026 USD ($) shares	May 21, 2026 EUR (€) shares	May 30, 2025 $ / shares shares	May 30, 2025 EUR (€) shares	Oct. 13, 2023 USD ($) $ / shares shares	Oct. 13, 2023 EUR (€) shares	Oct. 10, 2023 shares	Oct. 02, 2023 € / shares shares	Jul. 31, 2024 EUR (€)	Jun. 30, 2026 EUR (€) shares	Jun. 30, 2026 USD ($) shares	Jun. 30, 2026 EUR (€) shares	Sep. 30, 2025 EUR (€) shares	Jun. 30, 2025 shares	Sep. 30, 2024 shares	Jul. 03, 2024 $ / shares shares	Jun. 28, 2024 $ / shares shares
Disclosure Of Detailed Information About Equity [line items]
Shares repurchased of ordinary shares													3,927,344
Ordinary Shares
Disclosure Of Detailed Information About Equity [line items]
Number of ordinary shares					187,825,592	187,825,592		182,721,369		177,887,817	177,887,817	177,887,817	183,906,056	183,906,056	187,829,202
Ordinary Shares, Secondary Offering
Disclosure Of Detailed Information About Equity [line items]
Shares issued			16,100,000
Ordinary share price \| $ / shares			$ 52.5													$ 54	$ 54
Ordinary shares at a price \| $ / shares			$ 52.5
Number of shares exercised, option to purchase additional shares			2,100,000
Costs incurred \| €				€ 1.7					€ 1.9
Accelerated Share Repurchase
Disclosure Of Detailed Information About Equity [line items]
Costs incurred \| €										€ 0.2		€ 0.2
Shares repurchased of ordinary shares	6,022,282	6,022,282
Shares repurchased amount of ordinary shares	$ 250.0	€ 215.5									$ 16.1	14.2
Decrease in fair value \| €										€ 10.6		€ 10.6
Ordinary Shares
Disclosure Of Detailed Information About Equity [line items]
Shares issued					10,752,688	10,752,688
Initial public offering price \| $ / shares					$ 46
Total proceeds from IPO					$ 473.6	€ 450.0
Early repayment of borrowings \| €						100.0
Description of no par value ordinary shares								Prior to the IPO, the Company completed a capital reorganization. On October 2, 2023, the Company converted its share capital, comprised of 182,721,369 ordinary shares of €1.00 par value into 182,721,369 no par value ordinary shares.
Ordinary share price \| $ / shares			$ 50.93
Par value per share \| € / shares								€ 1
Shares repurchased of ordinary shares				3,927,344			5,648,465
Shares repurchased amount of ordinary shares \| €													€ 176.4
MidCo \| Ordinary Shares, Secondary Offering
Disclosure Of Detailed Information About Equity [line items]
Shares issued			14,000,000													16,100,000	16,100,000
Initial Public Offering
Disclosure Of Detailed Information About Equity [line items]
Underwriting commission fees \| €						19.8
Deferred offering costs \| €						3.0
USD Term Loan \| Ordinary Shares
Disclosure Of Detailed Information About Equity [line items]
Early repayment of borrowings					$ 450.0	€ 423.8