- One Aperture
- Onefurinthebox
- Ozark Softscape
- Oliver Chime
- Onur Vural
- Onur Vural and Leigh Christian
- Outplay Entertainment Ltd
- OneManTeam
- Overcurfew
- One Lives Left
- Orfeas Game Studio
- Outlaw Wars
- Oscar Celestini
- Omega Games
- One or Eight INC.
- Oneiric Entertainment LLC
- On The Wall Entertainment
- Oddly Shaped Pixels
- Oscar Kenneth Albero Ingles
- Open Sorcery Games
- Owlet
- OCP
- OpenWorldComics
- Over The Moon