Also see:
- ..Oblivion(1)
- ..Oddballz(1)
- ..Oddworld Series(2)
- ..Of Steamworks & Magick Obscura(1)
- ..OGame(5)
- ..Ogre Battle(2)
- ..Old Republic, The(36)
- ..Omega Stone, The(1)
- ..Once Upon a Knight(1)
- ..One Must Fall Series(1)
- ..Oni(1)
- ..Operation Flashpoint Series(4)
- ..Orbiter(5)
- ..Order of Dawn, The(2)
- ..Original Adventure(1)
- ..Ostfront 41-45(1)
- ..Outlaws(2)
- ..Outpost Series(1)
- ..Overlord Series(1)