Region | Title | System | Version | Edition | Languages | Serial | Status |
| Ocha no Ma Battle お茶の間バトル | PSX | | Bundled with Controller | | SLPM 86681 | |
| Oceans Below | 3DO | | Original | | | |
| Oceans Below The Software Toolworks Presents ... Oceans Below | MAC | | Original | | 2198620-590001 / I 073100, CDRM1103420 | |
| Oceans Below オーシャンズ・ビロウ | 3DO | | Original | | FZ-SJ2752 | |
| Oceans Below オーシャンズ・ビロウ | MAC | | Original | | MSC001 | |
| Ocean Jewels | PC | | Red Rocks | | | |
| Obut Pétanque 2 | XBOX360 | | Original | | W6-2008 | |
| Obsidian (Disc 5) | PC | | Original | | 11008 | |
| Obsidian (Disc 5) | PC | | Original, Complimentary Copy | | 11008 | |
| Obsidian (Disc 4) | PC | | Original, Complimentary Copy | | 11008 | |
| Obsidian (Disc 3) | PC | | Original, Complimentary Copy | | 11008 | |
| Obsidian (Disc 2) | PC | | Original, Complimentary Copy | | 11008 | |
| Obsidian (Disc 1) | PC | | Original | | 11008 | |
| Obsidian (Disc 1) | PC | | Original, Complimentary Copy | | 11008 | |
| Obsidian (Disc 5) オブシディアン | PC | | Original | | INR-1002 | |
| Obsidian (Disc 5) | MAC | | Original, Great Series | | INR-001, MKM-001 | |
| Obsidian (Disc 4) オブシディアン | PC | | Original | | INR-1002 | |
| Obsidian (Disc 4) | MAC | | Original, Great Series | | INR-001, MKM-001 | |
| Obsidian (Disc 3) オブシディアン | PC | | Original | | INR-1002 | |
| Obsidian (Disc 3) | MAC | | Original, Great Series | | INR-001, MKM-001 | |
| Obsidian (Disc 2) オブシディアン | PC | | Original | | INR-1002 | |
| Obsidian (Disc 2) | MAC | | Original, Great Series | | INR-001, MKM-001 | |
| Obsidian (Disc 1) オブシディアン | PC | | Original | | INR-1003 | |
| Obsidian (Disc 1) | MAC | | Original, Great Series | | INR-001, MKM-001 | |
| Obsidian (Disc 5) | PC | | Original | | | |
| Obsidian (Disc 4) | PC | | Original | | | |
| Obsidian (Disc 3) | PC | | Original | | | |
| Obsidian (Disc 2) | PC | | Original | | | |
| Obsidian (Disc 1) | PC | | Original | | | |
| ObsCure: The Aftermath | WII | | Beta | | | |
| ObsCure | XBOX | | Original | | MI-009 | |
| ObsCure (Disc 4) | PC | | Original | | | |
| ObsCure (Disc 3) | PC | | Original | | | |
| ObsCure (Disc 2) | PC | | Original | | | |
| ObsCure (Disc 1) | PC | | Original | | | |
| ObsCure | PC | | Original | | 71902134 | |
| ObsCure | XBOX | | Original | | MI-009 | |
| ObsCure | XBOX | | Original | | MI-009 | |
| ObsCure | XBOX | | Original | | MI-009 | |
| Oblivious Garden: Carmina Burana (Disc 2) (Music Disc) | PC | | Standard Edition | | | |
| Obitaemyj ostrov: Zemlyanin Обитаемый остров: Землянин | PC | | Original | | | |
| Obitaemyj ostrov: Chuzhoj sredi chuzhix Обитаемый остров: Чужой среди чужих | PC | | Original | | | |
| Obitaemyj ostrov Обитаемый остров | PC | | Original | | | |
| Obduction | MAC | | Kickstarter | | | |
| Ob"ekt 69: Mest' Krassera Объект 69: Месть Крассера | PC | | Original | | | |
| Ob"ekt 69: Kasablanka Объект 69: Касабланка | PC | | Original | | RUSSOBIT-M 2003/408 | |
| OASYS/Win V2.0 | FMT | | Original | | B28C7020 | |
| Oasis Road オアシスロード | PSX | | Original | | SLPS 01899 | |
| O'boy-jakten | PC | | Original | | | |
| O.R.B: Off-World Resource Base | PC | | Covermount | | | |
| O.D.T. | PC | | Original | | | |
| O.D.T. | PSX | | Original | | SLES-01409 | |
| O.D.T. | PSX | | Demo | | SLED-01574 | |
| O.D.T. | PSX | | Original | | SLES-01391 | |
| O.D.T. | PC | | Dice | | DCG 005509 | |
| O! Rety! Psoty Dudusia Wesołka | PC | | Playada Gier | | P_20265_03A_PL | |
| O Xephteris Taxideuei stin Ellada Ο Ξεφτέρης ταξιδεύει στην Ελλάδα | PC | | Original | | | |