| Obitus |
| Ochan no Oekaki Logic |
| Oda Nobunaga - Haou no Gundan |
| Oekaki Logic |
| Oekaki Logic 2 |
| Ogre Battle - The March of the Black Queen |
| Okamoto Ayako to Match Play Golf - Ko olina Golf Club in Hawai |
| Olivia's Mystery |
| Olympic Summer Games 96 |
| On the Ball |
| Ongaku Tsukuru - Kanadeeru |
| Onita Atsushi FMW |
| Onizuka Katsuya Super Virtual Boxing |
| Oomono Black Bass Fishing: Jinzouko Hen |
| Oozumou Tamashii |
| Operation Europe Path to Victory 1939-1945 |
| Operation Europe - Path to Victory 1939-45 |
| Operation Logic Bomb |
| Operation Thunderbolt |
| Oraga Land Shusai - Best Farmer Shuukaku-Sai |
| Oscar |
| Ossu!! Karatebu |
| Othello World |
| Otoboke Ninja Colosseum |
| Otogirisou |
| Out of This World |
| Out to Lunch |
| Outer World |
| Outlander |
