Companies
- Nvidia
- Obsidian Entertainment
- Odd Meter
- Oddworld Inhabitants
- Offworld Industries
- Omega Force
- One or Eight INC.
- OneMoreLevel
- OnePlus
- Open Lab Games
- Oreville Studios
- Other Ocean Interactive
- Ouka Studios
- Outright Games
- Overhaul Games
- Overkill Software
- Owlcat Games
- Owlchemy Labs
- Owned by Gravity
- Packom Interactive
- Paintbucket Games
- Panasonic
- Pandemic Studios
- Panic Button
- Parabole