| Title | Platform | Genre | Release Date |
|---|---|---|---|
| Open Water | PSP MOVIE | Other | na |
| Operation Barbarossa - The Struggle for Russia | PC | Strategy | Sep 10, 2010 |
| Operation Darkness | X360 | RPG | Jun 24, 2008 |
| Operation Flashpoint 2: Dragon Rising | PC | Other | Jan 1, 1970 |
| Operation Flashpoint: Cold War Crisis | PC | Action | Aug 30, 2001 |
| Operation Flashpoint: Dragon Rising | PC, X360, PS3 | Action | Oct 6, 2009 |
| Operation Flashpoint: Elite | XBOX | Action Adventure | Nov 9, 2005 |
| Operation Flashpoint: Red River | PC, X360, PS3 | Action | Jun 7, 2011 |
| Operation Flashpoint: Resistance | PC | Simulation | Jul 10, 2002 |
| Operation Mania | PC | Other | Nov 4, 2008 |
| Operation: Vietnam | DS | Action | Aug 14, 2007 |
| Opoona | WII | RPG | Mar 25, 2008 |
| Orbitor | PC | Action Adventure | na |
| Orc Attack: Flatulent Rebellion | PC, X360, PS3 | Action | Oct 8, 2013 |
| Orcs & Elves | DS | RPG | Nov 13, 2007 |
| Orcs Must Die! | PC, X360 | Other | Oct 12, 2011 |
| Orcs Must Die! 2 | PC | Action | Jul 30, 2012 |
| Order of War | PC | Strategy | Sep 22, 2009 |
| Order of War: Challenge | PC | Strategy | Mar 12, 2010 |
| Order Up! | WII, 3DS, PS3 | Strategy | Jul 22, 2008 |
| Ordyne | WII | Action | May 7, 2007 |
| Organ Trail: Director's Cut | PC | Adventure | Jan 1, 1970 |
| Organic Panic | PS3, PC, X360 | Puzzle | na |
| Orgarhythm | PSVITA | Strategy | Oct 23, 2012 |
| Original War | PC | Strategy | Dec 3, 2001 |