| Undersea Adventure (1993) | 108,274 | 78 |
| Undershadows (2025) | 1,153 | 2 |
| Underspace (2024) | 327,175 | 222 |
| Understanding, The Game (2020) | 2,563,851 | 162 |
| Undertale (2015) | 22,154,778,209 | 551,557 |
| Undertow (2007) | 4,856,106 | 492 |
| UNDERWARD (2025) | 895,197 | 288 |
| Underwater Diving (2024) | 116,782 | 25 |
| Underwater hunting (2018) | 6 | 3 |
| Underwater the Game (2009) | 349,895 | 47 |
| Underwater Wars (2021) | 6,783 | 16 |
| Underwater World (2021) | 22,395,800 | 336 |
| Underwater World - Idle Desktop Colony Building Simulator (2022) | 336 | 1 |
| Underway (2022) | 955,947 | 255 |
| Underworld Ascendant (2018) | 4,096,761 | 823 |
| Underworld Dungeon (2017) | 29,748 | 19 |
| Underworld Explorers (2024) | 0 | 0 |
| Underworld Idle (2021) | 2,719 | 20 |
| Underworld Island (2022) | 373,671 | 161 |
| Underworld Office (2020) | 2,369,293 | 386 |
| Underworld Overseer (2024) | 28,217 | 18 |
| Underworld Re: Card (2022) | 30 | 1 |
| Underworld: The Eternal War (2004) | 436,198 | 213 |
| Underwurlde (1984) | 68,143 | 72 |
| Underzone (2020) | 22,391 | 35 |
| Undesired Catch (2024) | 148,785 | 8 |
| Undesired Shift (2023) | 0 | 0 |
| UNDETECTED (2022) | 4,330,851 | 1,082 |
| The Undisputables: Online (2021) | 45,987 | 28 |
| Undivine (2025) | 7,431 | 42 |
| Undoing Evil (2022) | 0 | 0 |
| UnDungeon (2021) | 1,607,040 | 802 |
| Undusted: Letters from the Past (2025) | 229,850 | 148 |
| UnDuster (2024) | 59 | 3 |
| UNDYING (2021) | 38,018,993 | 7,410 |
| Undying Fortress (2025) | 230 | 1 |
| Undying Harvest (2024) | 0 | 0 |
| Unearned Bounty (2018) | 253,890 | 88 |
| Unearthed Inc: The Lost Temple (2016) | 15,154 | 17 |
| Unearthing Colossal (2016) | 6,505 | 9 |
| Unearthing Invasions (2024) | 0 | 0 |
| Unearthing Mars 2: The Ancient War (2018) | 61,991 | 121 |
| Unearthing Process (2019) | 0 | 0 |
| Uneasy Memories (2024) | 196 | 3 |
| Unending Dusk (2019) | 10,694 | 16 |
| Unending Galaxy (2016) | 0 | 0 |
| Unepic (2011) | 7,382,604 | 7,766 |
| The Unexpected Quest (2020) | 368,700 | 406 |
| Unexplored (2017) | 4,307,206 | 1,095 |
| Unexplored 2: The Wayfarer's Legacy (2021) | 610,081 | 296 |
| Unfabulous (2006) | 228,054 | 55 |
| Unfair Jousting Fair (2015) | 488,784 | 18 |
| Unfair Rampage: Knightfall (2025) | 753 | 10 |
| The Unfallens: Awakening (2023) | 1,852 | 48 |
| Unfinished Dream of All Living Ghost (2023) | 8,608,291 | 2,105 |
| The Unfinished Swan (2012) | 3,516,526 | 2,487 |
| The Unfinished Swan (2020) | 7,323,757 | 970 |
| Unfinished Tales: Illicit Love (2012) | 36,009 | 44 |
| Unfolded : Camellia Tales (2021) | 2,905 | 21 |
| Unfolded Cube (2024) | 36 | 2 |
| UNFOLLOW (2023) | 4,157,209 | 810 |
| Unforeseen Incidents (2018) | 1,019,565 | 1,387 |
| Unforetold: Witchstone (2024) | 237,603 | 52 |
| Unforgettable Voyage (2023) | 5,610 | 11 |
| Unforgettable You (2021) | 246 | 8 |
| Unforgivable: Eliza (2018) | 13,170 | 7 |
| Unforgiving Trials: The Space Crusade (2016) | 65 | 2 |
| Unforgiving: A Northern Hymn (2017) | 24,073,388 | 2,512 |
| Unforgotten: Ordinance (2025) | 9,079 | 62 |
| Unfortunate Spacemen (2020) | 7,377,199 | 1,275 |
| UnFound (2021) | 3,635 | 9 |
| Unhack (2015) | 12,648 | 51 |
| Unhack 2 (2017) | 759 | 13 |
| Unhappy Ever After (2017) | 4,557 | 19 |
| Unheard (2019) | 3,674,826 | 1,186 |
