| Undertale (2015) | 20,094,761,245 | 517,591 |
| Undertow (2007) | 4,851,360 | 488 |
| UNDERWARD (2025) | 730,024 | 116 |
| Underwater Diving (2024) | 101,385 | 23 |
| Underwater hunting (2018) | 6 | 3 |
| Underwater the Game (2009) | 299,034 | 43 |
| Underwater Wars (2021) | 6,783 | 16 |
| Underwater World (2021) | 22,265,724 | 297 |
| Underwater World - Idle Desktop Colony Building Simulator (2022) | 336 | 1 |
| Underway (2022) | 756,451 | 182 |
| Underworld Ascendant (2018) | 4,090,090 | 814 |
| Underworld Dungeon (2017) | 29,604 | 18 |
| Underworld Explorers (2024) | 0 | 0 |
| Underworld Idle (2021) | 2,710 | 20 |
| Underworld Island (2022) | 373,666 | 161 |
| Underworld Office (2020) | 2,368,385 | 378 |
| Underworld Overseer (2024) | 28,119 | 18 |
| Underworld Re: Card (2022) | 30 | 1 |
| Underworld: The Eternal War (2004) | 432,738 | 206 |
| Underwurlde (1984) | 66,550 | 67 |
| Underzone (2020) | 22,361 | 35 |
| Undesired Catch (2024) | 697 | 2 |
| Undesired Shift (2023) | 0 | 0 |
| UNDETECTED (2022) | 4,266,670 | 1,043 |
| The Undisputables: Online (2021) | 45,976 | 26 |
| Undivine (2025) | 6,773 | 34 |
| Undoing Evil (2022) | 0 | 0 |
| UnDungeon (2021) | 1,606,598 | 799 |
| UnDuster (2024) | 59 | 3 |
| UNDYING (2021) | 37,777,640 | 7,141 |
| Undying Harvest (2024) | 0 | 0 |
| Unearned Bounty (2018) | 253,890 | 88 |
| Unearthed Inc: The Lost Temple (2016) | 15,141 | 17 |
| Unearthing Colossal (2016) | 6,505 | 9 |
| Unearthing Invasions (2024) | 0 | 0 |
| Unearthing Mars 2: The Ancient War (2018) | 61,986 | 121 |
| Unearthing Process (2019) | 0 | 0 |
| Uneasy Memories (2024) | 196 | 3 |
| Unending Dusk (2019) | 10,694 | 16 |
| Unepic (2011) | 7,373,853 | 7,706 |
| The Unexpected Quest (2020) | 366,511 | 389 |
| Unexplored (2017) | 4,306,903 | 1,093 |
| Unexplored 2: The Wayfarer's Legacy (2021) | 609,743 | 295 |
| Unfabulous (2006) | 226,769 | 55 |
| Unfair Jousting Fair (2015) | 488,784 | 18 |
| The Unfallens: Awakening (2023) | 1,825 | 47 |
| Unfinished Dream of All Living Ghost (2023) | 8,531,052 | 2,032 |
| The Unfinished Swan (2012) | 3,514,809 | 2,459 |
| The Unfinished Swan (2020) | 7,322,004 | 966 |
| Unfinished Tales: Illicit Love (2012) | 35,942 | 43 |
| Unfolded : Camellia Tales (2021) | 2,905 | 21 |
| Unfolded Cube (2024) | 36 | 2 |
| UNFOLLOW (2023) | 0 | 0 |
| Unforeseen Incidents (2018) | 1,014,171 | 1,323 |
| Unforetold: Witchstone (2024) | 237,603 | 52 |
| Unforgettable Voyage (2023) | 514 | 9 |
| Unforgettable You (2021) | 246 | 8 |
| Unforgivable: Eliza (2018) | 13,159 | 7 |
| Unforgiving Trials: The Space Crusade (2016) | 65 | 2 |
| Unforgiving: A Northern Hymn (2017) | 24,064,592 | 2,466 |
| Unforgotten: Ordinance (2025) | 8,671 | 60 |
| Unfortunate Spacemen (2020) | 7,376,412 | 1,263 |
| UnFound (2021) | 3,635 | 9 |
| Unhack (2015) | 12,632 | 51 |
| Unhack 2 (2017) | 759 | 13 |
| Unhappy Ever After (2017) | 4,557 | 19 |
| Unheard (2019) | 2,967,342 | 1,128 |
| UNHEIM (2024) | 478,101 | 85 |
| Unhinged 2 (2025) | 0 | 0 |
| Unholy Alliance - Tower Defense (2021) | 859 | 16 |
| UnHolY DisAsTeR (2018) | 3,039,666 | 56 |
| Unholy Heights (2013) | 942,619 | 670 |
| Unholy Night: The Darkness Hunter (2017) | 396,219 | 130 |
| The Unholy Society (2020) | 80,812 | 46 |
| UnHolY ToRturEr (2019) | 0 | 0 |
