• OpenXcell Studio
• O'Stinky lab.
• OKAM Studio
• OSome Studio
• OxPrime Studio
• oneoreight
• OUTBOUNDS
• Oriku Inc
• Opus
• OhNoo Studio
• Oliver Keppelmüller
• Overgroup
• Orator Games
• Orbcreation
• Optical Override
• ORiGO GAMES
• Owl Green Sea
• Owlbear
• Oddrok
• OMAG
• Owl Studio
• Orch Star Studios
• Only Human Studios
• Operation Constellation