| Orendale (2025) | 0 | 0 |
| Oreshika: Tainted Bloodlines (2014) | 1,367,736 | 564 |
| Orestorm Factory (2023) | 916 | 2 |
| Oretachi Game Center Zoku: Time Pilot (2005) | 650 | 2 |
| Organ Quarter (2017) | 368,890 | 424 |
| Organ Trail (2010) | 2,349 | 10 |
| Organ Trail (2011) | 7,629,021 | 1,746 |
| Organ Trail: Director's Cut (2013) | 5,137,852 | 1,284 |
| Organs Please (2021) | 2,051,300 | 664 |
| Orgarhythm (2012) | 193,665 | 52 |
| Orgynizer (2022) | 16,406 | 20 |
| Ori and the Blind Forest (2015) | 249,605,085 | 100,635 |
| Ori and the Will of the Wisps (2020) | 108,971,890 | 70,839 |
| Oriental Blue: Ao no Tengai (2003) | 75,755 | 129 |
| Oriental Empires (2016) | 3,165,708 | 1,058 |
| Oriental Games (1990) | 882 | 16 |
| Oriental Valley (2024) | 47,324 | 36 |
| Origami Flight (2019) | 705 | 7 |
| Origami Lovers (2023) | 548 | 11 |
| Origami Treasure (2024) | 89 | 3 |
| Origin Of Destiny: Crimson Awakening (2016) | 144 | 2 |
| Original War (2001) | 2,196,438 | 2,363 |
| The Original Wizard (2023) | 93,511 | 26 |
| Orion (1983) | 6,749,162 | 40 |
| Orion Burger (1996) | 138,888 | 111 |
| The Orion Conspiracy (1995) | 85,918 | 67 |
| Orion: A Sci-Fi Visual Novel (2015) | 5,494 | 19 |
| ORION: Dino Beatdown (2012) | 4,269,009 | 166 |
| Orion: Prelude (2012) | 6,098,309 | 1,383 |
| Orion: The Eternal Punishment (2021) | 909 | 2 |
| Ork (1991) | 4,362,943 | 264 |
| ORKANA CONFLICT VR (2021) | 13,487 | 26 |
| Orly's Draw-A-Story (1997) | 39,821 | 14 |
| Ornament Express (2023) | 169 | 8 |
| Orphan (2018) | 15,370,510 | 695 |
| Orphan Age (2020) | 10,410,135 | 514 |
| Orphan Black: The Game (2017) | 7,334,417 | 20 |
| The Orphan Dreams (2016) | 147,799 | 22 |
| Orphan of the Petal (2019) | 15 | 1 |
| The Orphan: A Pop-Up Book Adventure (2023) | 426 | 10 |
| The Orphaned Soul (2018) | 0 | 0 |
| Orphen: Scion of Sorcery (2000) | 711,040 | 603 |
| The ORPHEUS Ruse (2015) | 604 | 3 |
| Orpheus's Dream (2019) | 11,747 | 46 |
| Orpheus: Fall For Eurydice (2022) | 510 | 1 |
| Orpiment (2021) | 3,845 | 4 |
| ORR (2020) | 117,474 | 43 |
| Orrstead (2023) | 301,314 | 50 |
| Orten Was The Case (2023) | 128,718 | 207 |
| Ortharion : The Last Battle (2023) | 24,040 | 110 |
| Orwell (2016) | 1,239,956 | 1,061 |
| Orwell's Animal Farm (2020) | 219,219 | 142 |
| Orwell: Ignorance is Strength (2018) | 354,675 | 356 |
| Orwell: Keeping an Eye On You (2016) | 942,777 | 929 |
| ORX (2022) | 3,082,327 | 656 |
| Oryks (2024) | 0 | 0 |
| Oscar (1993) | 415,054 | 76 |
| Oscar der Ballonfahrer (2010) | 5,397 | 8 |
| Oscar's World Tour (2011) | 1,067 | 3 |
| OscarWildeCard (2023) | 1 | 1 |
| Oscuria - The world of nightmares (2021) | 566 | 5 |
| Oseong-gwa Haneum (1993) | 155 | 2 |
| OSES (2017) | 24 | 2 |
| OshiRabu: Waifus Over Husbandos (2020) | 122,227 | 115 |
| Osiris: New Dawn (2016) | 48,524,609 | 10,985 |
| Osman (1996) | 452,019,316 | 3,861 |
| Osmos (2009) | 63,081,694 | 723 |
| OSR Unhinged (2010) | 0 | 0 |
| Ossuary (2015) | 22,679 | 50 |
| Ostalgie: The Berlin Wall (2018) | 418,677 | 307 |
| Osteoblasts (2021) | 39,371 | 134 |
| Ostranauts (2020) | 3,617,271 | 2,101 |
| Ostrich Island: Escape from Paradise (2015) | 6,248,800 | 86 |
| Ostrich Runner (2004) | 42,845 | 108 |
| Ostriv (2020) | 28,557,588 | 8,434 |
