| title | developer | year | game type | | pop. |
|---|
| Objective Force: Commander | DAS Entertainment | 2002 | Xbox | action/reflex | | | | |
| ObsCure | Hydravision | 2004 | Xbox | action/reflex Fantasy | image | | label | |
| Octane | Vivendi Games | 2002 | Xbox | action/reflex | | | | |
| Oddworld: Munch's Oddysee | Oddworld Inhabitants | 2001 | Xbox | Humorous | image | subject | label | |
| Oddworld: Stranger's Wrath | Oddworld Inhabitants | 2005 | Xbox | action/reflex adventure Fantasy | image | subject | label | |
| Oddworld: The Brutal Ballad of Fangus Klot | Oddworld Inhabitants | 2005 | Xbox | action/reflex Fantasy | | | label | |
| Open Season | Ubisoft Montreal | 2006 | Xbox | action/reflex Manga | | | | |
| Operation Flashpoint: Cold War Crisis | Bohemia Interactive | 2001 | Xbox | shooter strategy | | | label | |
| Operation Flashpoint: Elite | Bohemia Interactive | 2005 | Xbox | shooter | image | | label | |
| Orbz | 21-6 Productions | 2005 | Xbox | strategy | | | label | |
| Orchid | Argonaut Games | 2005 | Xbox | action/reflex | | | | |
| Otogi | From Software | 2002 | Xbox | action/reflex Fantasy | image | | label | |
| Otogi 2: Immortal Warriors | From Software | 2003 | Xbox | action/reflex Fantasy | image | subject | label | |
| Outlaw Chopper | Jarhead Games | 2005 | Xbox | action/reflex | | | | |
| Outlaw Golf | Hypnotix | 2002 | Xbox | sport | image | subject | label | |
| Outlaw Golf 2 | Hypnotix | 2004 | Xbox | sport | image | | label | |
| Outlaw Golf: 9 Holes of X-Mas | Hypnotix | 2003 | Xbox | sport | image | | label | |
| Outlaw Golf: Holiday Golf | Hypnotix | 2003 | Xbox | sport | image | | label | |
| Outlaw Tennis | Hypnotix | 2005 | Xbox | sport | image | | label | |
| Outlaw Volleyball | Hypnotix | 2003 | Xbox | fighting sport | image | subject | label | |
| Outlaw Volleyball: Red Hot | Hypnotix | 2003 | Xbox | action/reflex sport | image | | label | |
| OutRun2 | AM2 | 2004 | Xbox | racing/driving | image | subject | label | |
| OutRun2006: Coast 2 Coast | Sumo Digital | 2006 | Xbox | racing/driving | image | | label | |
| Over the Hedge | Edge of Reality | 2006 | Xbox | platformer Cartoon | image | | label | |
| Over The Top | Pitbull Syndicate | 2006 | Xbox | racing/driving | | | | |
| Ozzy's Black Skies | iROCK | 2006 | Xbox | action/reflex simulation | | | | |
