| Oceanhorn 2: Knights of the Lost Realm (2019) | 9,583,953 | 3,242 |
| Oceanhorn: Chronos Dungeon (2021) | 127,718 | 237 |
| Oceanhorn: Monster of Uncharted Seas (2013) | 32,174,194 | 10,222 |
| Oceanwork (2021) | 558,114 | 50 |
| Ocelot Sunrise (2023) | 11,645 | 30 |
| Ochitsubaki (2021) | 72 | 2 |
| Ocnus Theory (2023) | 387 | 21 |
| OCO (2021) | 81,001 | 99 |
| OctaFight (2020) | 2,900,423 | 72 |
| Octagon (2013) | 886,139 | 175 |
| Octahedron (2018) | 7,829,154 | 253 |
| Octane Remix (2023) | 420 | 13 |
| Octapolis (1987) | 7,549 | 8 |
| Octavio Camacho (2023) | 22 | 1 |
| Octo Vinctum: Saga of the Galactic Stardom War (2022) | 0 | 0 |
| October Night Games (2020) | 265,229 | 37 |
| Octodad (2010) | 350,584,993 | 5,279 |
| Octodad: Dadliest Catch (2014) | 437,357,411 | 11,508 |
| OctoFurry (2020) | 6,394 | 8 |
| Octogeddon (2018) | 269,362,091 | 1,448 |
| Octomania (2007) | 31,215 | 65 |
| Octopath Traveler (2018) | 145,482,350 | 89,841 |
| Octopath Traveler II (2023) | 37,627,633 | 44,184 |
| Octopath Traveler: Champions of the Continent (2020) | 16,768,070 | 9,861 |
| Octopede (2011) | 314 | 3 |
| OCTOPTICOM (2018) | 392 | 26 |
| Ocular Deprivation (2022) | 107 | 6 |
| Oda Nobunaga Den (1998) | 129,895 | 266 |
| Odallus: The Dark Call (2015) | 1,897,813 | 1,170 |
| Odama (2006) | 615,218 | 162 |
| Odania Sports Arena (2022) | 0 | 0 |
| Odd Realm (2019) | 1,428,626 | 360 |
| Oddballz (1996) | 29,949 | 17 |
| Oddinary Highway (2021) | 278 | 8 |
| Oddity Girls: Virtual World (2020) | 290 | 6 |
| Oddmar (2018) | 3,618,753 | 3,005 |
| Oddsparks: An Automation Adventure (2024) | 134,606 | 296 |
| Oddventure (2022) | 165,996 | 110 |
| Oddworld Adventures (1998) | 0 | 0 |
| Oddworld: Abe's Exoddus (1998) | 12,623,041 | 5,819 |
| Oddworld: Abe's Oddysee (1997) | 37,490,176 | 8,445 |
| Oddworld: Munch's Oddysee (2001) | 8,897,312 | 2,397 |
| Oddworld: New 'n' Tasty! (2016) | 27,307,641 | 10,054 |
| Oddworld: Soulstorm (2021) | 49,882,864 | 15,558 |
| Oddworld: Stranger's Wrath (2005) | 14,881,555 | 5,705 |
| Oddyssey: Your Space, Your Way (2023) | 88,674 | 167 |
| Odell Lake (1986) | 82,360 | 38 |
| Odin Sphere (2007) | 6,953,588 | 9,888 |
| Odin Sphere Leifthrasir (2016) | 9,982,166 | 15,916 |
| Odium (2022) | 119,846 | 76 |
| Odysseus Kosmos and his Robot Quest (2018) | 55,310 | 19 |
| Odyssey - The Story of Science (2017) | 0 | 0 |
| Odyssey of Dremid'ir (2024) | 40 | 4 |
| The Odyssey of the Mammoth (2022) | 1,478,481 | 243 |
| Odyssey: The Compleat Apventure (1980) | 9,340 | 8 |
| Odyssey: The Deep Space Expedition (2019) | 328 | 1 |
| Odyssey: The Search for Ulysses (2000) | 23,350 | 37 |
| Oedipus Dating Sim (2018) | 34 | 1 |
| Of Bird and Cage (2021) | 297,884 | 426 |
| Of Blades & Tails (2022) | 402,343 | 240 |
| Of Gods and Men: The Daybreak Empire (2018) | 4,864 | 18 |
| Of Guards And Thieves (2014) | 1,137,980 | 319 |
| Of Kings and Men (2016) | 3,456,225 | 295 |
| Of Light and Darkness: The Prophecy (1998) | 5,798 | 8 |
| Of Mice and Sand: Revised (2017) | 48,479 | 184 |
| Of Orcs and Men (2012) | 5,327,728 | 2,610 |
| of pawns & kings (2023) | 169 | 4 |
| Of Ships & Scoundrels (2019) | 3,372 | 14 |
| Off (2008) | 4,475,459 | 1,351 |
| Off Road (2008) | 633,477,480 | 30,119 |
| Off Road Challenge (1997) | 834,633 | 354 |
| Off Shore Warrior (1988) | 3,278 | 12 |
| Off The Road Unleashed (2021) | 13,601,445 | 1,399 |
| Off the Wall (1991) | 636,604 | 205 |
| Off-Road Drive (2011) | 16,708,745 | 1,911 |
