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- Oceania: fictional superstate in George Orwell's Nineteen Eighty-Four referring to England, the Americas, Australasia and southern Africa.
- Ornowitza: appeared in Violet Needham's Betrayer (1950).
- Orsinia: featured in Ursula Le Guin's Orsinian Tales and Malafrena.
- Osterlich: nation invaded by Bacteria and Tomainia in the movie The Great Dictator; obviously supposed to be Austria.
- Ovitznia: a republic in the Balkans from Road Rovers TV series.
Read more about this topic: List Of Fictional European Countries