iOS - O
- Ocean Tower
- Oceanhorn
- Oddwings Escape
- Off the Leash
- Office Jerk
- OGame
- Old Course
- OMG - TD!
- One Clue
- One Epic Knight
- One More Dash
- One More Line
- One Piece Treasure Cruise
- One Way Home
- Online Sniper League
- Optia
- Orbitum
- Orbity
- Orc - Vengeance
- Order and Chaos Online
- Order of Souls
- Oregon Trail
- Oregon Trail - American Settler
- Organ Trail - Director's Cut
- Original Gangstaz
- Osmos
- Out There
- Overkill
- Overkill 3
- Ow My Balls!