| Odyssey: The Compleat Apventure (1980) | 9,440 | 6 |
| Odyssey: The Deep Space Expedition (2019) | 328 | 1 |
| Odyssey: The Search for Ulysses (2000) | 23,546 | 37 |
| Oedipus Dating Sim (2018) | 34 | 1 |
| Oedipus/Antigone (2024) | 0 | 0 |
| Of Ash and Steel (2025) | 3,387,621 | 2,651 |
| Of Bird and Cage (2021) | 287,949 | 432 |
| Of Blades & Tails (2022) | 435,628 | 292 |
| Of Gods and Men: The Daybreak Empire (2018) | 6,398 | 18 |
| Of Guards And Thieves (2014) | 1,250,974 | 352 |
| Of Kings and Men (2016) | 3,345,469 | 285 |
| Of Lies and Rain (2025) | 378,879 | 297 |
| Of Light and Darkness: The Prophecy (1998) | 6,054 | 11 |
| Of Love And Sorrow (2016) | 58 | 1 |
| OF MICE AND SAND -REVISED (2018) | 17,619 | 116 |
| Of Mice and Sand: Revised (2017) | 33,572 | 88 |
| Of Orcs and Men (2012) | 6,199,014 | 3,070 |
| of pawns & kings (2023) | 936 | 5 |
| Of Ships & Scoundrels (2019) | 21,355 | 26 |
| Off (2008) | 3,864,022 | 1,304 |
| Off Course ELEMENTS of SPACE (2024) | 9 | 2 |
| Off Road (2008) | 607,496,772 | 29,497 |
| Off Road Challenge (1997) | 3,450,033 | 534 |
| Off Shore Warrior (1988) | 11,179 | 16 |
| Off The Record: Liberty Stone (2015) | 44,845 | 62 |
| Off The Record: The Art of Deception (2015) | 46,642 | 78 |
| Off the Record: The Final Interview (2015) | 32,486 | 57 |
| Off the Record: The Italian Affair (2014) | 44,540 | 100 |
| Off the Record: The Linden Shades (2013) | 28,986 | 43 |
| Off The Road Unleashed (2021) | 13,409,522 | 1,317 |
| Off the Wall (1991) | 1,540,576 | 220 |
| Off-Road Drive (2011) | 22,527,832 | 1,941 |
| Off-Road Paradise: Trial 4x4 (2017) | 627,824 | 53 |
| Off-Road Redneck Racing (2001) | 37,068 | 45 |
| Off-Road Super Racing (2016) | 194,287 | 39 |
| Off-Road Velociraptor Safari (2008) | 35,986 | 19 |
| Off-World Interceptor (1994) | 116,830 | 224 |
| Offendron Warrior (2018) | 130 | 6 |
| Offensive Combat (2017) | 1,010,801 | 272 |
| Offensive Dimensions (2017) | 23 | 1 |
| OFFERING APP (2023) | 123,719 | 53 |
| Office After Hours (2025) | 943,667 | 119 |
| Office Battle (2015) | 23,789,027 | 114 |
| Office Disorders (2010) | 205 | 2 |
| Office Fight (2024) | 53,387 | 57 |
| Office Girls and Games (2023) | 303 | 6 |
| Office Management 101 (2022) | 68,447 | 62 |
| Office Nightmare Chapter 1 Alpha (2024) | 167 | 1 |
| Office Overloaded (2025) | 42 | 1 |
| The Office Quest (2018) | 13,333,023 | 650 |
| Office Run (2022) | 906 | 26 |
| Office Simulator (2020) | 142,903 | 157 |
| The Office Type (2025) | 143 | 7 |
| Officers (2008) | 1,239,770 | 222 |
| Official Formula One Racing (1999) | 15,467 | 30 |
| OffRoad Drive Desert (2016) | 25,986,104 | 1,215 |
| Offroad Driving Simulator 4x4 (2017) | 1,749,283 | 114 |
| Offroad Legends (2012) | 1,831,014 | 302 |
| Offroad Legends 2 (2014) | 3,014,409 | 874 |
| Offroad Mini Racing (2021) | 26,333 | 6 |
| Offroad Racing (2019) | 1,613,132 | 655 |
| Offroad Thunder (1999) | 79,224 | 98 |
| Offroad Track Simulator 4x4 (2015) | 9,457 | 12 |
| Offroad Truck Racing (2022) | 36,655 | 16 |
| Offroad: Dead Planet (2023) | 275 | 8 |
| Offside (2022) | 11,770,651 | 259 |
| Offspring Fling (2012) | 867,990 | 207 |
| Offworld Trading Company (2016) | 9,544,510 | 3,169 |
| Oftalmogarden (2021) | 0 | 0 |
| OG Puzzlers: Synthwave Astronauts (2024) | 0 | 0 |
| OG Puzzlers: Synthwave Dinosaurs (2024) | 8 | 2 |
| OG Puzzlers: Synthwave Knights (2024) | 0 | 1 |
| OG Puzzlers: Synthwave Monsters (2024) | 0 | 1 |
| OGame (2002) | 15,166,482 | 1,426 |
| Ogre (1986) | 14,750 | 47 |
