| OMSI: The Bus Simulator (2011) | 98,172,234 | 8,774 |
| Omurice Next Time (2024) | 118 | 4 |
| OMUSUBI (2024) | 125,040 | 56 |
| On a Roll (2017) | 3,596,058 | 389 |
| On A Roll 3D (2015) | 2,802 | 21 |
| On a Summer Night (2025) | 5 | 2 |
| On Air (2021) | 116,043,860 | 3,496 |
| On Dark Terms (2023) | 98,416 | 53 |
| On My Own (2016) | 184,857,813 | 1,856 |
| On my own: A Hot Isekai Adventure (2023) | 0 | 0 |
| On Point (2024) | 9,827,523 | 754 |
| On Reflection (2007) | 117,987 | 10 |
| On Rusty Trails (2016) | 66,505 | 74 |
| On the Ball (1993) | 6,712,719 | 506 |
| On the Dragon Wings - Birth of a Hero (2022) | 1,047 | 7 |
| On the Hunt (2024) | 878,037 | 442 |
| On The Job (2023) | 3,713,807 | 356 |
| On the Peril of Parrots (2023) | 602 | 6 |
| On The Road: Truck Simulator (2017) | 6,891,552 | 2,699 |
| On the Run: Rogue Heroes (2024) | 801 | 1 |
| On The Wind's Breath (2025) | 0 | 0 |
| On Your Hands (2022) | 242,132 | 34 |
| On Your Tail (2024) | 1,230,070 | 357 |
| On-Court Tennis (1984) | 14,639 | 14 |
| Once a Porn a Time 2 (2024) | 0 | 0 |
| Once a Tale (2024) | 12,073 | 56 |
| Once Again (2022) | 33,545,189 | 2,979 |
| Once Bitten, Twice Dead! (2015) | 162,842 | 35 |
| Once Human (2024) | 127,268,106 | 44,910 |
| Once on a windswept night (2017) | 1,453 | 34 |
| Once upon a Dungeon - Infinity (2025) | 3,509 | 17 |
| Once upon a Dungeon II (2023) | 944 | 10 |
| Once Upon a Jester (2022) | 293,443 | 309 |
| Once Upon A Puppet (2025) | 265,917 | 368 |
| Once Upon a Rogue's Tale (2024) | 34,338 | 33 |
| Once Upon A Siege (2022) | 0 | 0 |
| Once Upon a Time in the Colony (2021) | 0 | 0 |
| Once Upon A Time: Abracadabra (1991) | 446 | 7 |
| Once Upon A Time: Little Red Riding Hood (1991) | 1,700 | 4 |
| Once Upon an All Hallow's Eve (2017) | 394 | 9 |
| Onde (2022) | 9,622,121 | 1,207 |
| One (1997) | 5,646,291 | 578 |
| One (2005) | 30,144 | 24 |
| One Bear Army (2024) | 42 | 2 |
| One Boss One Fight (2024) | 29,845 | 32 |
| ONE BTN BOSSES (2024) | 21,677 | 53 |
| One Bullet left (2018) | 156,057 | 21 |
| One Chance (2010) | 48,742,557 | 548 |
| One Clone Left (2016) | 0 | 0 |
| One Day in London (2016) | 73,750 | 169 |
| One Deck Dungeon (2018) | 746,778 | 472 |
| One Dog Story (2017) | 55,818 | 217 |
| One Dreamer (2020) | 35,340 | 113 |
| One Dreamer (2022) | 82,662 | 97 |
| One Drunken Knight (2022) | 426 | 12 |
| One Eleven (2023) | 560,466 | 473 |
| One Epic Game (2011) | 268,251 | 53 |
| One Escape (2021) | 12,672,002 | 575 |
| One Eyed Kutkh (2017) | 59,202 | 114 |
| One Finger Death Punch (2013) | 24,963,000 | 3,347 |
| One Finger Death Punch 2 (2019) | 2,815,672 | 2,122 |
| One Hand Clapping (2020) | 66,765,296 | 3,850 |
| One Hit KO (2017) | 221,482 | 46 |
| One Hour And A Straight Line (2024) | 0 | 0 |
| One Hour One Life (2018) | 95,151,859 | 3,384 |
| One Hundred Ways (2015) | 104,590 | 48 |
| One Iced Latte With Your Breast Milk, Please! (2025) | 6,677 | 13 |
| One Last Chance (2016) | 1,239,016 | 128 |
| One Last Crane (2022) | 0 | 0 |
| One Last Day (2015) | 22,764 | 18 |
| One Last Time (2022) | 44,580,361 | 1,810 |
| One Late Night: Deadline (2014) | 5,915,085 | 209 |
| One Lonely Outpost (2022) | 1,228,390 | 996 |
| One Long Night with the Circleheads (2024) | 13 | 1 |
| One Man and His Droid (1985) | 30,047 | 40 |
