| Number None |
| O-Games |
| O3 Entertainment |
| Oberon Media |
| Obsidian Entertainment |
| Oddworld Inhabitants |
| ODENIS Studio |
| Odin Game Studio |
| Old School Games |
| Oldblood |
| Omega Force |
| OmiyaSoft |
| Orbital Media |
| Orion |
| OSome Studio |
| Ostrich Banditos |
| OSW Games |
| Outerlight |
| Outrage Games |
| Outrage Studios |
| Over the Moon |
| Oxygen Interactive |
| Page 44 Studios |
| PAM Development |
| Pandemic Studios |
| Papaya Studio |
| Papyrus Racing Games |
| Paradigm Entertainment |
| Paradox Development |
| Paradox Interactive |
| Parallax Arts Studio |
| Pendulo Studios |
| People Can Fly |
| Perfect World Entertainment |
| PES Productions |
| Petroglyph |
| Phantagram |
| Phantom EFX |
| Phantomery Interactive |
| Phenomic |
| Philos Labs |
| Phoenix Interactive |
| Phoenix Online Studios |
| Pieces Interactive |
| Pipedream Interactive |
| PipeWorks |
| Piranha Bytes |
| Pitbull Syndicate |
| Pivotal Games |
| PixelStorm |
| Planet Moon Studios |
| Plastic |
| Plastic Reality Technologies |
| PlatinumGames |
| Play Ten Interactive |
| PlayDead |
| Playful Entertainment |
| Playlogic |
| Point of View |
| Pollux Gamelabs |
