• OPQAM
• Octopus Tree
• Omega Point Games
• oneIMMERS
• ouka-ichi-mon.inc
• O.P. Games
• Olly Whillans
• Oodlescube
• Octopi is not a Word
• Outcorp
• OnFire Games
• Ovid Works
• Orange_Juice
• Overidon Omnimedia
• Oh, a Rock! Studios
• Over the Top Games
• onomatope*
• Ozzie Sneddon
• Ominous Entertainment
• Oneshark
• Oldblood
• Olmo Castrillo
• opti
• onoboss