| Ojiv (2023) | 78 | 2 |
| OK Golf (2017) | 85,846 | 122 |
| OK K.O.! Lakewood Plaza Turbo (2016) | 14,195,386 | 208 |
| OK K.O.! Let's Play Heroes (2018) | 17,580,784 | 989 |
| Okabu (2011) | 113,160 | 109 |
| Okage: Shadow King (2001) | 2,076,425 | 2,632 |
| Ōkami (2006) | 93,812,485 | 41,429 |
| Ōkamiden (2010) | 12,000,579 | 2,094 |
| Okashi na Shima no Peter Pan: Sweet Never Land (2011) | 3,400 | 3 |
| Okhlos (2016) | 3,195,255 | 430 |
| Old Future: Post-Apocalyptic Times (2022) | 1,419 | 5 |
| Old Gods Rising (2020) | 90,397 | 120 |
| The Old Man and His Cat (2024) | 0 | 0 |
| Old Man's Journey (2017) | 6,423,223 | 2,981 |
| Old School Musical (2018) | 1,629,708 | 836 |
| Old School Racer (2010) | 700 | 6 |
| Old School RuneScape (2013) | 555,802,997 | 43,854 |
| Old Time Baseball (1995) | 4,441 | 17 |
| Old World (2020) | 22,552,226 | 6,670 |
| OldMaidGirl (2017) | 61,495 | 12 |
| Oldowan (2023) | 7,457 | 23 |
| OLDTV (2017) | 459,961 | 153 |
| Olija (2020) | 1,343,281 | 743 |
| Olija (2021) | 428,881 | 394 |
| Oliver's Adventures in the Fairyland (2019) | 64,078 | 33 |
| Ollie King (2004) | 115,150 | 40 |
| Ollie's Follies (1984) | 8,107 | 15 |
| Olliefrog Toad Skater (2024) | 64,459 | 46 |
| OlliOlli (2014) | 2,125,623 | 601 |
| OlliOlli World (2021) | 17,075 | 2 |
| OlliOlli World (2022) | 15,300,105 | 3,516 |
| OlliOlli2: Welcome to Olliwood (2015) | 4,781,351 | 848 |
| OlliOlli: Switch Stance (2016) | 84,400 | 43 |
| Olmang Jolmang Paradise (1995) | 2,607 | 10 |
| OloFight (1999) | 7,199 | 4 |
| Olympia Soiree (2020) | 0 | 0 |
| Olympia Soirée (2021) | 8,317,641 | 455 |
| Olympia Soiree - Nintendo Switch (2020) | 75 | 1 |
| Olympic Basketball (2019) | 154,169 | 19 |
| Olympic Decathlon (1980) | 27,193 | 20 |
| Olympic Games Tokyo 2020 - The Official Video Game (2019) | 54,669,703 | 3,337 |
| Olympic Games: Atlanta 1996 (1996) | 3,616 | 11 |
| Olympic Gold (1992) | 1,361,958 | 205 |
| Olympic Hockey '98 (1998) | 78,929 | 77 |
| Olympic Soccer (1996) | 65,611 | 120 |
| Olympic Summer Games (1996) | 369,079 | 267 |
| Om Nom: Run (2020) | 88,827,273 | 10,120 |
| OM6N (2017) | 106 | 4 |
| Omae Wa Mou Shindeiru (2018) | 3,154,459 | 443 |
| Omar Sharif on Bridge (1992) | 4,676 | 6 |
| Omega (1989) | 338,597 | 151 |
| Omega Boost (1999) | 1,119,380 | 515 |
| Omega Crafter (2024) | 1,130,643 | 294 |
| Omega Enfo Bla (2010) | 29 | 1 |
| Omega Fighter (1989) | 93,466 | 230 |
| Omega Five (2008) | 113,603 | 93 |
| Omega Labyrinth Life (2019) | 1,354,352 | 488 |
| OMEGA PATTERN - VISUAL NOVEL (2017) | 350 | 3 |
| Omega Quintet (2014) | 2,528,585 | 5,055 |
| Omega Race (1981) | 97,533 | 157 |
| Omega Run (1984) | 4,762 | 6 |
| The Omega Stone (2003) | 28,920 | 14 |
| Omega Strike (2017) | 1,252,413 | 713 |
| Omega Warp (2023) | 1,643 | 15 |
| Omen Exitio: Plague (2018) | 43,322 | 172 |
| Omen of Sorrow (2018) | 2,061,780 | 1,621 |
| Omensight (2018) | 1,013,625 | 2,065 |
| Omerta: City of Gangsters (2013) | 3,276,602 | 1,893 |
| Ometron (1983) | 265 | 1 |
| OMFG: One Million Fatal Guns (2021) | 16,972 | 139 |
| OMG-Z (2011) | 46,674 | 57 |
| Omi Oh My AI (2022) | 56 | 1 |
| Omikron: The Nomad Soul (1999) | 14,537,237 | 1,110 |
| Ominous Horizons: A Paladin's Calling (2001) | 15,242 | 15 |
| Omni Axes (2023) | 0 | 1 |
