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- Okishima Island: from the novel Battle Royale by Koushun Takami and the film Battle Royale by Kinji Fukasaku
- Olympus: an artificial island nation, run by genetic modified humans and advanced technology, Appleseed manga
- Oracle Island: a paradimensional island that connects Earth, in our universe, to Areo in the universe 'Xejjaszuh', via the Bermuda Triangle, in The Turbulence Series.
- Orange Islands: an extensive island chain consisting of various active islands, Pokémon anime
- Otter Island: a sentient island from Oren Otter's multimedia series Otter Island
- Outset Island:, the home of Link in the Nintendo Gamecube Game The Legend of Zelda: The Wind Waker
- Oxbay: a small colony island in Pirates of the Caribbean video game
Read more about this topic: List Of Fictional Islands