| title | developer | year | game type | | pop. |
|---|
| Of Orcs and Men | Cyanide;Spiders | 2012 | X360 | action/reflex Fantasy | image | | label | |
| Ōgon Musōkyoku X | 07th Expansion;Alchemist | 2011 | X360 | fighting | | | label | |
| Omega Five | Natsume | 2008 | X360 | shooter Science Fiction | image | | label | |
| Onechanbara: Bikini Samurai Squad | Tamsoft | 2006 | X360 | beat 'em up | image | subject | label | |
| Open Season | Ubisoft Montreal Studios;Ubisoft Quebec City | 2006 | X360 | platformer | image | | | |
| Operation Darkness | Success | 2007 | X360 | strategy role-play Fantasy | image | | label | |
| Operation Flashpoint: Dragon Rising | Codemasters | 2009 | X360 | shooter | image | subject | label | |
| Operation Flashpoint: Red River | Codemasters | 2011 | X360 | action/reflex shooter | | | label | |
| Orbitron: Revolution | Firebase Industries | 2011 | X360 | shooter Science Fiction | | | label | |
| Orcs Must Die! | Robot Entertainment | 2011 | X360 | action/reflex strategy Fantasy | image | | label | |
| Otomedius Excellent | Konami | 2011 | X360 | shooter Manga | image | | label | |
| Otomedius G | Konami | 2008 | X360 | shooter | image | | label | |
| Outland | Housemarque | 2011 | X360 | action/reflex platformer | image | subject | label | |
| Outpost Kaloki X | NinjaBee | 2005 | X360 | manag./econ. Cartoon | image | | label | |
| Outrun Online Arcade | Sumo Digital | 2009 | X360 | racing/driving | image | | label | |
| Over G | Taito Corporation | 2006 | X360 | simulation flight | image | subject | label | |
| Overlord | Triumph Studios | 2007 | X360 | action/reflex adventure Fantasy | image | | label | |
| Overlord II | Triumph Studios | 2009 | X360 | action/reflex adventure Fantasy | image | | label | |
| Overlord: Raising Hell | Triumph Studios | 2008 | X360 | action/reflex adventure Fantasy | image | | label | |
