| Obelisk | WORLD | 2025-08 |
Horatiu.NYC | Unlicensed |
| Oblique Strategies | WORLD | |
| Unlicensed |
| Oddworld Adventures | EU | 1998-12 |
GT Interactive | Commercial |
| Oddworld Adventures | US | 1998-12 |
GT Interactive | Commercial |
| Oira Jajamaru! Sekai Daibouken | JP | 1990-09 |
Jaleco | Commercial |
| Olympic Skier | WORLD | |
| Unlicensed |
| Olympic Summer Games | EU | 1996-06 |
Black Pearl Software | Commercial |
| Olympic Summer Games | US | 1996-06 |
Black Pearl Software | Commercial |
| Oni | WORLD | 2022-01 |
GB Studio Central | Unlicensed |
| Oni II - Oni Densetsu | JP | 1992-02 |
Banpresto | Commercial |
| Oni III - Kuro no Hakaishin | JP | 1993-02-26 |
Banpresto | Commercial |
| Oni IV - Kijin no Ketsuzoku | JP | 1994-03-11 |
Banpresto | Commercial |
| Oni IV - Kijin no Ketsuzoku | JP | 1994-03-11 |
Banpresto | Prototype |
| Oni V - Oni wo Tsugumono | JP | 1995-03 |
Banpresto | Commercial |
| Onigashima Pachinkoten | JP | 1991-02-08 |
Coconuts Japan | Commercial |
| Operation C | US | 1991-02 |
Ultra Games | Commercial |
| Operation C | WORLD | 1987 |
Ultra Games | Commercial |
| Opossum a la Mode | WORLD | 2024-01 |
Oxcyde | Unlicensed |
| Osawagase! Penguin Boy | JP | 1990-08-08 |
Natsume | Commercial |
| Othello | EU | 1991-10 |
Kawada | Commercial |
| Othello | JP | 1990-02-09 |
Kawada | Commercial |
| Othello World | JP | 1994-09-30 |
Tsukuda Original | Commercial |
| Otogibanashi Taisen | JP | 1995-08-04 |
Yojigen | Commercial |
| Otto's Ottifanten - Baby Bruno's Alptraum | EU | 1998 |
Infogrames | Commercial |
| Otto's Ottifanten - Baby Bruno's Alptraum | EU | 1998 |
Infogrames | Prototype |
| Out of Gas | US | 1992-08 |
FCI | Commercial |
| Out of Gas | US | 1992-08 |
FCI | Prototype |
| Out on a Limb | WORLD | |
| Unlicensed |
| Outburst | JP | 1993-03-26 |
Konami | Commercial |
| Oyatsu Quiz Mogu Mogu Q | JP | 1997-09-26 |
Starfish | Commercial |