| Overboundn | Developer | |
| Overflow | Developer | |
| Overgame Studio | DeveloperPublisher | |
| Overgrown | Developer | |
| Overhead Games | Developer | |
| Overkill Software | Developer | |
| Overmax Studios | Developer | |
| Overpowered Games | Developer | |
| Overseas | Developer | |
| Overtired_FOX | Developer | |
| Overtold | Developer | |
| OverwaterGames Official | Developer | |
| OverworkedStudios | Developer | |
| Overworks | DeveloperPublisher | |
| Overworld Galaxy | Developer | |
| Ovid Works | Developer | |
| Ovidiu Barac | Developer | |
| Ovine by Design | DeveloperPublisher | |
| Ovosonico | Developer | |
| OwT | Developer | |
| Owen Ayers | Developer | |
| Owen Brunette | Developer | |
| Owen Deery | Developer | |
| Owen Emry | Developer | |
| Owen Heinz | Developer | |
| OwenM45 | Developer | |
| OwenSenior | Developer | |
| OwenTheBell | Developer | |
| Owhno | Developer | |
| Owl Nest Studios | Developer | |
| Owl Sanctuary Studios | Developer | |
| OwlTechInteractive | Developer | |
| OwllCraft | Developer | |
| Owlor | Developer | |
| OwlyCode | Developer | |
| Owned by Gravity | Developer | |
| Ox Flame Game Dev | Developer | |
| Oxbane Project | Developer | |
| Oxeye Game Studio | DeveloperPublisher | |
| Oxford Digital Enterprises | Developer | |
| Oxford Digital Enterprises (Kevin R. Ayre) | Developer | |
| Oxford Digital Enterprises (Michael Fox) | Developer | |
| Oxford Digital Enterprises Ltd. | Developer | |
| Oxford Mobius | Developer | |
| Oxford Softworks | DeveloperPublisher | |
| OxfordLucrezia | Developer | |
| OxiWan | Developer | |
| Oxidental Games | Developer | |
| Oxonian Games | Developer | |
| Oxygen Games | DeveloperPublisher | |