| Title | Year | Genre |
|---|---|---|
| O.B.Y. 1 | ???? | Arcade |
| Oath, The | ???? | Shooter |
| Oberon 69 | 1990 | Arcade |
| Obitus | ???? | Adventure |
| Obliteratives, The | 1993 | Arcade |
| Obliterator | ???? | Action |
| Oblivion | ???? | Shooter |
| Obsession | ???? | Action |
| Obstickle | ???? | Arcade |
| Odds on Favourite | 1998 | Arcade |
| Odyssey | 1995 | Action |
| Off Shore Warrior | ???? | Action |
| Offence | 1994 | Shooter |
| Official Everton FC Intelligensia, The | ???? | Quiz |
| Official Honda NSR-R Simulator, The | 1989 | Moto racing |
| Og | ???? | Platform |
| Ogre | ???? | Strategy |
| Oh No! More Lemmings | ???? | Puzzle |
| Oids | 2014 | Spaceship |
| Oil Barons | 1992 | Management |
| Oil Imperium | ???? | Management |
| Oilmania | 1990 | Arcade |
| Okey | 1991 | Puzzle |
| Oklib's Revenge | 1992 | Adventure |
| Okrety | 1994 | Puzzle |
| Oktagon | ???? | Arcade |
| Okuzan | 1993 | Puzzle |
| Olempiad '92 | 1992 | Sports |
| Olimpiada 96 | 1996 | Sports |
| Oliver and Company | 1989 | Arcade |
| Olympique de Marseille | 1993 | Soccer |
| Olympus | 1990 | Arcade |
| Omar Sharif's Bridge | ???? | Cards |
| Omega | ???? | Action |
| Omni-Play Basketball | ???? | Basketball |
| Omni-Play Horse Racing | ???? | Bets |
| Omnicron Conspiracy | ???? | Action |
| On The Ball League Edition | ???? | Soccer |
| On The Ball World Cup Edition | ???? | Soccer |
| On the Road | 1990 | Management |
| One on One | ???? | Basketball |
| One Step Beyond | 1993 | Adventure |
| One to One Match | ???? | Puzzle |
| Onslaught | ???? | Action |
| Oo-Topos | 1986 | Adventure |
| Ooops Up | ???? | Arcade |
| Ooze | ???? | Adventure |
| Operacion Fallida | 2022 | Action |
| Operation Cleanstreets | ???? | Action |
| Operation Com-bat | ???? | Strategy |
