Companies
- Offworld Industries
- Ojom GmbH
- Okomotive
- Old Moon
- Omega Force
- OneMoreLevel
- Oni Press
- OnLive
- OP Productions
- Open World
- Orange
- Orange Pixel
- Oreville Studios
- ORiGO Games
- OSome Studio
- Ossian Studios
- Other Ocean Interactive
- Otherside Entertainment
- Outright Games
- Outside Xbox
- Outspark Inc
- Over The Moon
- OverBorder Studio
- Overhaul Games
- Overkill Software
- Ovosonico
- Owl Cave
- Owlcat Games
- Owlchemy Labs
- Oxide Games
- Packom Interactive
- Panache Digital Games
- Panasonic
- Pandemic Studios
- Panic
- Panic Button
- PanicBarn
- Papergames
- Parabole
- Paradox Development Studio
- Paradox Interactive
- Paradox North
- Paradox Tectonic
- Parallel Studio
- Paramount
- Paramount Digital Entertainment
- Paramount Pictures
- Parsec Productions
- Passtech Games
- Paypal