| Oxygen GamesEU | Publisher | |
| Oxygen GamesPAL | Publisher | |
| Oxygen Interactive | DeveloperPublisher | |
| Oxygen Studios | Developer | |
| Oxygene Media | DeveloperPublisher | |
| Oyadi | Developer | |
| Oyedoyin | Developer | |
| Oyuncu112 | Developer | |
| Oz Club | DeveloperPublisher | |
| Oz Software | Developer | |
| Ozark Softscape | Developer | |
| Ozark Software | Developer | |
| Ozdeger | Developer | |
| OziSoft AU | Publisher | |
| Ozla Pictures | Developer | |
| O~3 Entertainment | Publisher | |
| O~3 EntertainmentNA | Publisher | |
| P Jackson | Developer | |
| P Knecht | Developer | |
| P&P Marketing | Publisher | |
| P-PAMda | Developer | |
| P-Squared Productions | Developer | |
| P-Studio | Developer | |
| P. Sudon | Developer | |
| P.I.S.C. | Developer | |
| P.J. Soft | DeveloperPublisher | |
| P.J. Software (Carlos Coronel) | Developer | |
| P.J. Software (Josoft, Carlos Coronel) | Developer | |
| P.K. McManus | Developer | |
| P.Rahjoe | Developer | |
| P.S. ASSA | Developer | |
| P.S.S. | Publisher | |
| P.Z.Karen Co. | Developer | |
| P.Z.Karen Co. Development Group | Developer | |
| P0lter | Developer | |
| P1X | Developer | |
| P1xelFang | Developer | |
| P2 Games | DeveloperPublisher | |
| P2P Pte. Ltd. | Publisher | |
| P32nicky | Developer | |
| P4thog3n | Developer | |
| PAL | Publisher | |
| PAL Developments | Developer | |
| PAL Developments (Dave Thompson) | Developer | |
| PAL Developments (Dave Thompson, Richard Morton) | Developer | |
| PAL Developments (David Spicer, Jason Brashill) | Developer | |
| PAL Developments (Kevin Nichol, Chris Moorehouse) | Developer | |
| PAL Developments (Mark Wallace, Richard Morton, Sean Conran) | Developer | |
| PAL Developments (Mongee Boswell) | Developer | |
| PAL Developments (Richard Stevenson) | Developer | |