Steam Deck games: O
- "Otherworldly: Beginning of the Rift" Pre-AlphaPlayable
- >observer_Playable
- O.B.O.LVerified
- O2Jam : The BeginningPlayable
- OafmatchPlayable
- OakenVerified
- Oaken TowerVerified
- OASIS: TokyoPlayable
- Obama MazePlayable
- ObductionPlayable
- ObenseuerPlayable
- Oberak (Prelude)Playable
- OBEYPlayable
- Obey the Insect GodVerified
- Obey the Voice™Verified
- Objects in SpacePlayable
- ObliteracersPlayable
- Oblivion MaidenVerified
- Oblivion OverridePlayable
- Oblivity - Find your perfect SensitivityPlayable
- ObludiaPlayable
- Oboro no IchiPlayable
- Obscure II (Obscure: The Aftermath)Playable
- ObscuritasPlayable
- Obscurite Magie: The Blood of KingsPlayable
- Obscurite Magie: The City of SinPlayable
- ObservePlayable
- ObservePlayable
- Observe and ReportPlayable
- Observer: System ReduxVerified
- Obsessed : Night ShiftPlayable
- ObsideoPlayable
- ObsidianVerified
- Obsidian PrincePlayable
- ObsurityPlayable
- OccludePlayable
- OccultPlayable
- OccultoVerified
- Ocean Cleaner IdlePlayable
- Ocean DesolationPlayable
- Ocean Is Home : Island Life SimulatorVerified
- Ocean Keeper Co-op Drill MultiplayerPlayable
- Ocean Keeper: Dome SurvivalVerified
- Ocean PlanetPlayable
- Ocean's HeartPlayable
- OceaneersPlayable
- Oceanhorn 2: Knights of the Lost RealmVerified
- Oceanhorn: Chronos DungeonVerified
- Oceanhorn: Monster of Uncharted SeasVerified
- OceansPlayable
- Oceanside WhispersPlayable
- Ocnus TheoryVerified
- Octahedron: Transfixed EditionVerified
- OctametaPlayable
- Octodad (Student Edition)Playable
- Octodad: Dadliest CatchVerified
- OctogeddonVerified
- OCTOPATH TRAVELER 0Verified
- OCTOPATH TRAVELER IIVerified
- OCTOPATH TRAVELER™Playable
- OCTOPinbsPlayable
- Odd Adventure of Chub, Color, 23 and YouVerified
- Odd Guy Meets Odd Farmers - Comedy Boys Love (BL) Visual NovelVerified
- Odd RealmPlayable
- Odd RemedyPlayable
- Odd TownPlayable
- ODDADAVerified
- OddBallersPlayable
- ODDCOREVerified
- OddFauna : Secret of the TerrabeastVerified
- Oddsparks: An Automation AdventureVerified
- OddventureVerified
- Oddworld: Abe's Exoddus®Playable
- Oddworld: Abe's Oddysee®Playable
- Oddworld: Munch's OddyseeVerified
- Oddworld: New 'n' TastyPlayable
- Oddworld: Soulstorm Enhanced EditionPlayable
- Oddworld: Stranger's Wrath HDPlayable
- OdinfallVerified
- OdiumPlayable
- Odysseus Kosmos and his Robot Quest: Episode 1Playable
- Odyssey - The Story of SciencePlayable
- OeufPlayable
- Of Ash and SteelPlayable
- Of Bird and CageVerified
- Of Blades & TailsVerified
- Of Guards And ThievesPlayable
- Of Life and LandPlayable
- Of Orcs And MenPlayable
- of the DevilVerified
- OFFVerified
- Off The GridPlayable
- Off TrailPlayable
- Off-Road: Redneck RacingPlayable
- OFFBEATPlayable
- OFFERING APPVerified
- Office After HoursVerified
- Office BattlePlayable
- office chair curlingVerified
- Office LifePlayable
- Office SimulatorPlayable
- Offroad ManiaVerified
- Offroad Mechanic SimulatorPlayable
- Offspring Fling!Playable
- Offworld Trading CompanyPlayable
- OgrePlayable
- Ogre Chambers 2222Verified
- Ogre TaleVerified
- Ogu and the Secret ForestVerified
- Oh Baby KartVerified
- Oh Darling! I Hate To Tell You This...Playable
- Oh DeerPlayable
- OH MY GOD, LOOK AT THIS KNIGHTVerified
- Oh My GodheadsPlayable
- Oh My Gore!Playable
- Oh, honey! Anime clicker!Verified
- Oh, you touch my balls ( ͡° ͜ʖ ͡°)Playable
- Oh! Edo TownsVerified
- Oh! Fuse BoxPlayable
- Oh...Sir! The Hollywood RoastPlayable
- OHVPlayable
- OikVerified
- Oik Memory 2Verified
- Oil EmpirePlayable
- Oil WarsPlayable
- OK BoomerPlayable
- Okami HDVerified
- Okashi TowersPlayable
- Okinawa RushPlayable
- Okko The ExiledPlayable
- Old Coin Pusher FriendsPlayable
- Old Coin Pusher Friends 2Playable
- Old Coin Pusher Friends 3Playable
- Old Coin Pusher GaidenPlayable
- Old Man's JourneyVerified
- Old Market RestoredPlayable
- Old Market SimulatorPlayable
- Old SchoolVerified
- Old School MusicalVerified
- Old School RallyVerified
- Old School RPGPlayable
- Old School RuneScapePlayable
- Old SkiesVerified
- Old WorldPlayable
- oldbI tyt ?Verified
- OldowanPlayable
- OLDTVPlayable
- Olga - Episode 1Verified
- Olga Doesn't DiePlayable
- OlijaVerified
- Olive's Art-VenturePlayable
- OliviaPlayable
- OlliOlliVerified
- OlliOlli WorldVerified
- OlliOlli2: Welcome to OlliwoodPlayable
- Olympia RisingPlayable
- OlympiusPlayable
- OMEGA 6 The Triangle StarsVerified
- Omega CrafterPlayable
- Omega Labyrinth LifePlayable
- Omega StrikersPlayable
- Omelet You CookVerified
- OmenPlayable
- Omen Exitio: HungerPlayable
- Omensight: Definitive EditionVerified
- OMFG: One Million Fatal GunsPlayable
- OMG WordsPlayable
- Omni LinkPlayable
- OmniblastPlayable
- OmnibulletPlayable
- OmnoPlayable
- Omoide Ni Kawaru Kimi Memories OffPlayable
- OMORIPlayable
- On a RollPlayable
- On A Roll 3DPlayable
- On Dark TermsPlayable
- On my own: A Hot Isekai AdventurePlayable
- On Rusty TrailsVerified
- On The BrinkPlayable
- On the Dragon Wings - Birth of a HeroPlayable
- On the front lineVerified
- On The JobVerified
- On The Road - The Truck SimulatorPlayable
- On the Run: Rogue HeroesVerified
- On TrackPlayable
- On Your HandsPlayable
- On Your TailVerified
- Once a TalePlayable
- Once AgainVerified
- Once AlivePlayable
- Once in FlowerlakePlayable
- Once Upon a GalaxyPlayable
- Once Upon A KATAMARIVerified
- Once Upon A PuppetVerified
- Once Upon a Rogue's TalePlayable
- Once Upon a ShellVerified
- Once Upon an All Hallow's EvePlayable
- OndePlayable
- One Boss One FightPlayable
- ONE BTN BOSSESVerified
- One Deck DungeonVerified
- One Deck GalaxyPlayable
- One Dollar SimulatorPlayable
- One DreamerVerified
- One Finger Death PunchVerified
- One Finger Death Punch 2Playable
- One Gun GuyPlayable
- One Hand ClappingVerified
- One in a KrillionPlayable
- One King Is EnoughPlayable
- One Last BreathPlayable
- One Last ClipPlayable
- One Last HandPlayable
- One Last RaidPlayable
- One Life ClickerPlayable
- One Lonely OutpostVerified
- One Many NobodyPlayable
- One Military CampPlayable
- One Million CoinsPlayable
- One More Dungeon 2Playable
- One More Gate : A Wakfu LegendPlayable
- One More IslandPlayable
- One Move AwayVerified
- one night, hot springsVerified
- One Piece Burning BloodVerified
- ONE PIECE ODYSSEYPlayable
- One Piece Pirate Warriors 3Playable
- ONE PIECE World SeekerVerified
- ONE PIECE: Grand GourmetPlayable
- ONE PIECE: PIRATE WARRIORS 4Verified
- One Piece: Unlimited World Red - Deluxe EditionPlayable
- One Room NightmarePlayable
- One Step From EdenVerified
- One Tower DefensePlayable
- One Turn KillPlayable
- One Way HeroicsPlayable
- One Way UpPlayable
- One Way: The ElevatorVerified
- One Week With The MafiaVerified
- One Wheel GuyVerified
- One-armed cookPlayable
- One-armed robberPlayable
- One-Eyed LikhoVerified
- One-inch TacticsVerified
- ONE.Playable
- OneBit AdventurePlayable
- Onee Chanbara ORIGINPlayable
- OneirosPlayable
- ONENELLEMOOPlayable
- Oneons: PrisonersPlayable
- OneRoom ―Yui Hanasaka Memorial―Verified
- OneShot: World Machine EditionVerified
- oneway.exe: Module 1.0Playable
- ONI : Road to be the Mightiest OniPlayable
- Onigiri Shop SimulatorVerified
- Onigo HunterPlayable
- Oniken: Unstoppable EditionPlayable
- Onikira - Demon KillerPlayable
- Onimusha 2: Samurai's DestinyVerified
- Onimusha: WarlordsVerified
- Onimusha: Way of the SwordPlayable
- ONINAKIPlayable
- Oniria CrimesPlayable
- Online SparklerPlayable
- Only Down!Playable
- Only FortressPlayable
- Only IfPlayable
- Only Lead Can Stop ThemPlayable
- Only Up: With FriendsPlayable
- Only Up!Playable
- Only Up! 1Playable
- Only Way is DownVerified
- Only YouVerified
- OnslaughtPlayable
- OntotisPlayable
- oOPlayable
- Ooble GardensPlayable
- OobletsVerified
- ÖooVerified
- Oops, I Said Yes?!Playable
- Oops!!! I Slept With Your MomPlayable
- Ooze KeeperVerified
- Oozi: Earth AdventureVerified
- OPEC IDLEPlayable
- Open CountryVerified
- Open HexagonPlayable
- Open RoadsVerified
- Open SorceryVerified
- Open Sorcery: Sea++Playable
- Open Wheel Manager 2Playable
- OpenFrontPlayable
- OpenTTDPlayable
- Operation : Strike & SecurePlayable
- Operation Abyss: New Tokyo LegacyPlayable
- Operation Babel: New Tokyo LegacyPlayable
- Operation MarakudjaPlayable
- Operation Night StrikersPlayable
- Operation Save the Girl: Code XPlayable
- Operation Sheep DefenseVerified
- Operation Space ForcePlayable
- Operation STEELVerified
- Operation ValorPlayable
- Operation: Harsh DoorstopPlayable
- Operation: Harsh Doorstop "Closed Beta"Playable
- Operation: New EarthPlayable
- Operation: OutbreakPlayable
- Operation: TangoPlayable
- OPERATORPlayable
- Operator OverloadPlayable
- Operencia: The Stolen SunPlayable
- OppidumVerified
- Optical Shop SimulatorPlayable
- Opus MagnumPlayable
- OPUS: Echo of Starsong - Full Bloom EditionVerified
- OPUS: Prism PeakVerified
- OPUS: Rocket of WhispersPlayable
- OPUS: The Day We Found EarthPlayable
- ORVerified
- Oracle 5000Playable
- Oracle of Forgotten TestamentPlayable
- Orange - The Annoying ClickerVerified
- Orange SeasonPlayable
- OrangebloodVerified
- Orb BreakerVerified
- Orb of CreationPlayable
- Orbi Universo IIPlayable
- Orbit PuzzleVerified
- Orbit ZeroPlayable
- ORBITALPlayable
- Orbital ClashPlayable
- OrbiTankPlayable
- OrbitectPlayable
- OrbitmineVerified
- Orbo's OdysseyVerified
- OrborunPlayable
- OrbosPlayable
- Orbox CPlayable
- OrbWarsPlayable
- Orc IncrementalPlayable
- Orc SurvivorPlayable
- Orc Tales: Olgob The BoldVerified
- OrcdomPlayable
- OrcinUS: Orca Pod RescuePlayable
- Orcish SkiesPlayable
- Orcs Must Die!Playable
- Orcs Must Die! 2Playable
- Orcs Must Die! 3Verified
- Orcs Must Die! DeathtrapVerified
- Ord.Verified
- Ordeal of Princess ErisVerified
- ORDER 13Playable
- Order from CaosVerified
- Order from Caos 2Verified
- Order of Battle: World War IIPlayable
- Order of the Sinking StarVerified
- Orders of MagnitudePlayable
- Ore Factory Squad ⛏️Playable
- OrebitsPlayable
- OreboundPlayable
- OrePlantPlayable
- Organ Trail: Director's CutPlayable
- Organize my ShopPlayable
- OrgynizerPlayable
- Ori and the Blind ForestVerified
- Ori and the Blind Forest: Definitive EditionVerified
- Ori and the Will of the WispsPlayable
- Oriental EmpiresPlayable
- Origament: A Paper AdventureVerified
- Original WarPlayable
- Oriko DaysPlayable
- Orion TrailPlayable
- ORIX!Playable
- Orphan of the PetalPlayable
- OrpheusPlayable
- Ortharion : The Last BattlePlayable
- Ortheo's Interdimensional Jam SessionPlayable
- Orwell: Ignorance is StrengthPlayable
- Orwell: Keeping an Eye On YouPlayable
- Orwell's Animal FarmVerified
- ORXPlayable
- orzPlayable
- Oscura: Lost LightPlayable
- Oscuro Blossom's GlowVerified
- OshiRabu: Waifus Over HusbandosVerified
- OshiRabu: Waifus Over Husbandos ~Love･or･die~Verified
- Osminog Adventures - The Lost IslandPlayable
- OsmosPlayable
- OstaPlayable
- Ostalgie: The Berlin WallPlayable
- OstensibleVerified
- OsteoblastsPlayable
- OstranautsVerified
- OstrivPlayable
- Oswald's AdventurePlayable
- Otaku and Bubbly Girl - 游戏宅与青春女Playable
- Otaku's AdventurePlayable
- Othello Let's GoVerified
- Other SubmarinePlayable
- OtherwarPlayable
- Otherworld LegendsPlayable
- Otome the ExorcistPlayable
- OtterettoPlayable
- Otterly LostPlayable
- OTXOVerified
- OUPlayable
- Ouija RumoursPlayable
- Our Adventurer GuildVerified
- Our AscentPlayable
- Our Brief EternityPlayable
- Our Lovely EscapePlayable
- Our Ordinary HomePlayable
- Our Two Bedroom StoryPlayable
- Our Wonderful WorldVerified
- OurlandsPlayable
- OuroborosPlayable
- OurosVerified
- Out and AboutPlayable
- Out of ActionPlayable
- Out Of HandsVerified
- Out of LineVerified
- Out of OrbitPlayable
- Out of OrderPlayable
- Out of OrePlayable
- Out of ReachPlayable
- Out of Reach: Treasure RoyalePlayable
- Out of SightVerified
- Out of Stock!Playable
- Out of the MistPlayable
- Out of the Park Baseball 26Playable
- Out of the Park Baseball 27Playable
- Out There SomewhereVerified
- Out There: Oceans of TimePlayable
- Out ZoneVerified
- OutboundVerified
- OutbreakPlayable
- Outbreak IslandPlayable
- Outbreak The Fedora Files: What Lydia KnowsPlayable
- OUTBUDDIES DXVerified
- Outcast - A New BeginningPlayable
- Outcast - Second ContactPlayable
- Outcast Tales: The First JourneyPlayable
- Outer TerrorPlayable
- Outer WildsVerified
- OuterversePlayable
- OutfieldPlayable
- OutholdPlayable
- Outland KingdomsPlayable
- OUTLANDERPlayable
- OutlandersVerified
- OutlastPlayable
- Outlast 2Playable
- Outlaws + Handful of Missions: RemasterVerified
- Outlive 25Playable
- Outlying IslandsPlayable
- OUTMINERVerified
- OutpackedPlayable
- OutpathPlayable
- Outpath: First JourneyPlayable
- OutpostPlayable
- outpost4Playable
- OutRage: Fight FestVerified
- Outrider MakoVerified
- OUTRIDERSPlayable
- OutRoad FuryPlayable
- Outrun ThemVerified
- OutshinePlayable
- outside the doorPlayable
- OutskirtsPlayable
- Outward Definitive EditionVerified
- Outworld StationPlayable
- Ova MagicaVerified
- Over 9000 Zombies!Playable
- over the hillVerified
- Over the NetPlayable
- Over The PhonePlayable
- Over The Top: WWIPlayable
- OVER THE TOWERPlayable
- Overboard!Verified
- OverbowedVerified
- OverclockedVerified
- Overclocked: The AclockalypsePlayable
- Overcome Your Fears - CaretakerPlayable
- OvercookedVerified
- Overcooked! 2Verified
- Overcooked! All You Can EatPlayable
- Overcrowd: A Commute 'Em UpPlayable
- OverDrift FestivalPlayable
- Overdrive WarfarePlayable
- OverdungeonVerified
- OvergrownPlayable
- OvergrowthVerified
- OverlandVerified
- OverloadPlayable
- Overload Playable Teaser 3.0Playable
- OverlootingPlayable
- Overlord : Nobody know victory better than mePlayable
- Overlord IIPlayable
- OVERLORD: ESCAPE FROM NAZARICKVerified
- Overlord™Playable
- OvermorrowPlayable