• ONSTER PLANET Corp.
• omegen
• Odd1 Apps
• Oppana Games
• OneTen Games
• O'ol Blue Inc.
• OranCG
• Outright Games
• Outer Brain Studios
• OctoberRaven
• Origin8
• Oovee® Game Studios
• Obscurasoft
• OVERKILL Software
• Octopirate Games
• OBLIVISION
• onyonvoid
• Overpowered Games
• Orlyapps
• OPENCAP STUDIO
• Overhaul Games
• Ocean Media LLC
• Opium Pulses Entertainment
• Orion Games