Nintendo Wii - O
- Oboro Muramasa
- Obscure - the Aftermath
- Obscure 2
- Ocean Commander
- Octomania
- Oekaki Logic
- Offroad Extreme
- Offshore Tycoon
- Ogre Battle - the March of the Black Queen
- Okami
- One Piece - Unlimited Adventure
- One Piece - Unlimited Cruise 1
- One Piece - Unlimited Cruise 2
- One Piece Unlimited Adventure
- One Piece Unlimited Cruise - Episode 1
- One Piece Unlimited Cruise - Episode 2
- One Piece Unlimited Cruise - Episode 2 - Mezameru Yuusha
- Onechanbara - Bikini Zombie Slayers
- Oneechanbara Revolution
- Onslaught
- Open Season
- Opera for Wii
- Operation Wolf
- Opoona
- Order Up!
- Order!
- Ordyne
- Oregon Trail
- Ougon no Kizuna
- Overlord - Dark Legend
- Override
- Overturn