Related Party Disclosures - Summary of Consolidated Financial Statements Include Financial Statements of Opthea Limited and Subsidiaries (Details)	12 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2023
Vegenics Pty Ltd
Disclosure Of Equity Interest In Subsidiaries [Line Items]
Ownership percentage in subsidiary	100.00%	100.00%	100.00%
Opthea US Inc
Disclosure Of Equity Interest In Subsidiaries [Line Items]
Ownership percentage in subsidiary	100.00%	100.00%	100.00%

The proportion of ownership interest in a subsidiary attributable to the entity. [Refer: Total for all subsidiaries [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2024-01-01
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-URIDate 2024-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2024-01-01
-Paragraph 16
-Subparagraph b
-Clause iii
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2024-01-01
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-Subparagraph c
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