Games starting with O
- Oaken TowerPC
- ObamaPC
- Obama Boss FightPC
- OBEYPC
- Object NPC
- Objects in SpacePC
- ObscurePC
- Obscure II (Obscure: The Aftermath)PC
- ObsideoPC
- OccultPC
- Occupy Mars: The GamePC
- Ocean World: Eden Crafters ProloguePC
- Octodad: Dadliest CatchPC
- Oddsparks: An Automation AdventurePC
- Of Guards And ThievesPC
- Off The GridPC
- Off-Road DrivePC
- Offworld Trading CompanyPC
- Oh Baby KartPC
- Oh DeerPC
- Oh...Sir! PrototypePC
- Oh...Sir! The Hollywood RoastPC
- Oh...Sir!! The Insult SimulatorPC
- Oil RushPC
- Old Coin Pusher FriendsPC
- Old Coin Pusher Friends 2PC
- Old Market SimulatorPC
- Old SchoolPC
- Old School MusicalPC
- Old School RuneScapePC
- Old WorldPC
- OlliOlli2: Welcome to OlliwoodPC
- Omega CrafterPC
- Omega StrikersPCPSXboxSwitch
- OmegalodonPC
- OmniBusPC
- On a RollPC
- On-Together: Virtual Co-WorkingPC
- Once HumanPCPSXbox
- Once Upon a GalaxyPC
- Once Upon A KATAMARIPC
- One Deck DungeonPC
- One Hour One LifePC
- One Military CampPC
- ONE PIECE Bounty RushPC
- One Piece Burning BloodPC
- One Piece Pirate Warriors 3PC
- ONE PIECE: PIRATE WARRIORS 4PC
- ONE PUNCH MAN: A HERO NOBODY KNOWSPC
- One Step From EdenPC
- One Troll ArmyPC
- One Way To DiePC
- One-armed cookPC
- One-armed robberPC
- OnigiriPC
- OnirismPC
- Online: 404PC
- Only Climb: Better TogetherPC
- Only Up: With FriendsPC
- OnmyojiPC
- ONRAIDPC
- OnrushPSXbox
- OnsetPC
- OnwardPC
- OogliansPC
- Open CountryPC
- OpenFrontPC
- Operation: Harsh DoorstopPC
- Operation: New EarthPC
- Operation: TangoPC
- Operation: Tango - Friend PassPC
- OPERATORPC
- OrbitalsSwitch
- Orcs Must Die! 2PC
- Orcs Must Die! 3PC
- Orcs Must Die! DeathtrapPC
- Order of Battle: World War IIPC
- Ore Factory Squad ⛏️PC
- OreboundPC
- Oriental EmpiresPC
- Original WarPC
- ORION: PreludePC
- OthelloSwitch
- Otherworld LegendsPC
- Out of ActionPC
- Out of AmmoPC
- Out of OrePC
- Out of ReachPC
- Out of Reach: Treasure RoyalePC
- Out of SpacePC
- Out of the Park Baseball 26PC
- Out of the Park Baseball 27PC
- OutboundPC
- Outbreak: The New NightmarePC
- OUTBRKPC
- Outlaws + Handful of Missions: RemasterPC
- Outlaws of the Old WestPC
- OutpathPC
- Outpost ZeroPC
- Outpost: Infinity SiegePC
- OUTRIDERSPCPSXbox
- Outward Definitive EditionPCPSXbox
- Outworld StationPC
- Over 9000 Zombies!PC
- over the hillPC
- Over The Top: WWIPC
- OvercookedPC
- Overcooked! 2PCPSXboxSwitch
- Overcooked! All You Can EatPC
- OverDrift FestivalPC
- OverFieldPC
- OvergrowthPC
- OverloadPC
- Overlord: Fellowship of EvilPC
- OverstepPC
- OverthrownPC
- Overwatch: Legendary EditionPSXboxSwitch
- Overwatch®PCPSXboxSwitch
- OxyRailPC
- Ozymandias: Bronze Age Empire SimPC