Games starting with O
68 series
- Observer: System Redux
- Occupy Mars: Prologue
- Octodad: Dadliest Catch8.44
- OCTOPATH TRAVELER8.19
- OCTOPATH TRAVELER II
- Oddworld: Abe's Oddysee
- Oddworld: New 'n' Tasty8.13
- Of Guards And Thieves
- Oh...Sir!! The Insult Simulator8.24
- Okami HD8.37
- Old School RuneScape
- OLDTV
- Olympic Games Tokyo 2020 – The Official Video Game
- OMON Simulator
- OMORI8.74
- OMSI 2: Steam Edition
- Once in Yaissor
- One-armed robber
- One Finger Death Punch
- One Piece Pirate Warriors 3
- ONE PIECE: PIRATE WARRIORS 48.42
- OneShot8.77
- One Troll Army
- One Way Heroics
- Only If7.51
- Only Up
- Onmyoji
- ONRAID
- Onward
- OpenTTD
- Operation Flashpoint: Dragon Rising7.84
- Operation Flashpoint: Red River7.71
- Operation: Harsh Doorstop
- Operation: Tango
- Opus Magnum8.46
- Orcs Must Die!8.47
- Orcs Must Die! 28.46
- Orcs Must Die! 3
- Orcs Must Die! Unchained7.68
- Order of Battle: World War II7.98
- Ori and the Blind Forest8.59
- Ori and the Blind Forest: Definitive Edition8.64
- Ori and the Will of the Wisps8.73
- ORION: Prelude
- Orqa FPV.SkyDive
- Orwell: Keeping an Eye On You8.35
- Osiris: New Dawn
- Our Life: Beginnings & Always
- Outcore: Desktop Adventure
- Outer Wilds8.67
- Outland8.01
- Outlast8.72
- Outlast 28.45
- OUTRIDERS
- Outward Definitive Edition
- Overcast - Walden and the Werewolf
- Overcooked8.35
- Overcooked! 28.43
- Overcooked! All You Can Eat
- Overgrowth
- Overlord8.37
- Overlord II8.22
- Overlord: Raising Hell
- OVR Advanced Settings
- OVR Toolkit - Desktop Overlay
- Owlboy8.09
- Oxenfree8.38
- Oxygen Not Included8.73