Homepage: Marisa-Chan/UA_source
Inspiration: Urban Assault
Developer: Anton Yarcev

Homepage: csinkers/ualbion
Inspiration: Albion

Homepage: duion.com/games/uebergame/main
Inspirations: ARMA 2, ARMA 3, ARMA: Armed Assault
Download: duion.com/games/uebergame/downloads
Developers: Alex Piola, ZOD

Homepage: ufo2000.sourceforge.net
Inspirations: X-COM: Apocalypse, X-COM: Terror from the Deep, X-COM: UFO Defense
Developers: Fomka, Siarhei Siamashka

Homepages: ufoai.org/wiki/News, ufoai
Media: UFO: Alien Invasion
Inspirations: X-COM: Apocalypse, X-COM: Terror from the Deep, X-COM: UFO Defense
Download: ufoai.org/wiki/Download
Developers: aDuke1, Alexander Tishin, anthraxx, bayo, BTAxis, CH, DarkRain, DarkRainX, drane, Duke, Forest Hale, geever, Holger 'ShipIt' Gellrich, hwoarangmy, Ihor Hrytsenko, Internecivus Raptus, Kostia Romanov, Kracken, Maksym Kobieliev, Martin Gerhardy, Muton-UfoAI, Nate Wright, NateWr, radius75, Rudolfo Pinewood, rxadmin, Sander van Grieken, Sergii Pylypenko, Solbu, Tamás Fehérvári, Tron, UFO: Alien Invasion, UFOAI

Homepages: www.ularn.org, ularn
Inspiration: Larn
Developers: Ethan Dicks, Josh Bressers, Scott Neugroschl, Thomas Huth

Homepage: www.pygame.org/project-UlDunAd-1140-.html
Developers: Nicholas Hydock, stump

Homepage: u5redux.wordpress.com
Inspiration: Ultima V: Warriors of Destiny
Developers: Brad Hannah, MrMan4th

Homepages: www.ultimatestunts.nl, ultimatestunts
Inspiration: Stunts
Downloads: www.ultimatestunts.nl/index.php?page=2, ultimatestunts/files
Developers: Borbola Balázs, CJP, M Gagnon, Neil Zanella

Homepages: usdx.eu, ultrastardx
Inspiration: SingStar
Download: usdx.eu/downloads
Developers: Alexander, Alexander Sulfrian, basisbit, Benedikt Krueger, blindy, Brian Chalega da Silva, brianch, brunzel, Canni, Dawid Dembowski, djazz, Eddie, ePirat, Felix Kaechele, GaryCXJk, Hermann Döppes, Holger Kuhn, jay binks, joachimdieterich.com, Jose Riha, K.-M. Schindler, Karl-Michael Schindler, lotan_rm, Markus, Markus Böhning, MezzoX, Mog, mota23, RattleSN4K3, s09bQ5, shazzzzam, Simon Ruderich, Stefan L., Tobias Gunkel, Valérianne, Whiteshark

Homepage: usplay.net
Inspiration: SingStar
Developers: achimmihca, barbeque-squared, basisbit, Dex, Michiel

Homepage: lukaszjakowski.pl/project,20,mario-cpp.html
Inspiration: Super Mario
Developers: Tony Narlock, Łukasz Jakowski

Homepage: Archive: 20180816232325/https://markdamonhughes.com/Umbra
Download: Archive: 20180816232325/https://markdamonhughes.com/Umbra/#download

Homepages: umoria.org, beej.us/moria
Media: Umoria
Downloads: umoria.org/download, beej.us/moria/files
Developer: Michael R. Cook

Homepages: yairm210/UnCiv, yairm210.itch.io/unciv
Inspiration: Civilization V
Developers: 9kgsofrice, AdityaMH, Alexander Korolyov, Am-per-Sand, armandberger, Arthur van der Staaij, Augusto Oliveira, Brian Gainor, Bryan W. Weber, coding-human, Coruna, Daniel Bälz, dic1911, Duan Tao, F4R3LB3ST, Fantaziu Ion, Federico Luongo, Freshy, GGGuenni, Giuseppe D'Addio, givehub99, HadeanLake, Jack Rainy, jnecus, Kensvin, Kentalot, LeMoonStar, lishaoxia1985, logic, lyrjie, Marerjh, mrimvo, NoNZeeZ, Oheto, Oleg, paontv, pikkolpk, Prosta4okua, proteus-anguinus, RadioMagnetofonStereofoniczny, ravignir, rayray61, RCalleti, Roumaan, Runo Hawk, SimonCeder, SomeTroglodyte, SpacedOutChicken, StepanIvasyn, sulai, sveckarel, u-ndefine, vhj, Vladimir Tanakov, Voytee, Väinö Mäkelä, wrov, Xander Lenstra, Yair Morgenstern, Yann

Homepages: uwadv.sourceforge.net, uwadv
Inspiration: Ultima Underworld 1
Download: uwadv.sourceforge.net/index.php?page=download
Developers: Aisha Fenton, Dirk Manders, Jim Cameron, Kasper Fauerby, Michael Fink, Radoslaw Grzanka, vividos, Willem Jan Palenstijn

Homepage: hankmorgan/UnderworldExporter
Inspirations: Ultima Underworld 1, Ultima Underworld II: Labyrinth of Worlds
Developer: hankmorgan

Homepage: DavidGriffith/uninvited
Inspiration: Uninvited
Developer: David Griffith

Homepage: unitystation.org
Inspiration: Space Station 13
Downloads: store.steampowered.com/app/801140/unitystation, unitystation/unitystation/releases?after=0.1.3.1
Developers: [Redacted], a_heckin_canadian, actions-user, Adalino, Akbadain29, Akronymus, aleios, Alessandro Romancino, Alex, Alex Evgrashin, Alvin, Andre Odendaal, Aranclanos, Atner, Autumn, Azzy, Badgers2, Baran Barut, Bebob, Bobtheapple, Bod9001, Bonfire, Buldinn, C4BRA, Cardioxo, Cassie Villarreal, chairbender, Christian Bender-Saebelkampf, Christopher Moore, CodeKalias, coolcat1711, Copern, craftxbox, cvdva, dapocalypse, DeeJayhX, dillonfurey, DMCraftGit, Doobly, DRAbsol, drneuris, DTraitor, Elijah Burshtein, Em3rgencyLT, Emma3DSS, Epicworlds, Eugene, Evan Rogers, Fax, Fiftyllama, Foma, Fortune117, Francesco, fuele, Gavin Rowan, Gil, Gilles, goman0, h3killa, Harcourt1, Hex, HiddenKnowledge, Human Being, Humonitarian, jackpotttt, Jacob Sweeten, James, James Simonson, JaytleBee, Jeremy Liberman, JesterX666, Jibbajabbafic, Joel Hedtjärn, Jorge Martinez, Josh M., Justin Trotter, Keir Smith, Kjeld Schouten-Lebbing, ktndrnl, Lennoxicon, Leonard K, Lizurt, LukaErCaiman, Max, MaxIsJoe, Michael Bolland, Michael Nader, Michał Czemierowski, Moon, Moses, MrAsbestos, Necromunger, Nick M., Nikolas Petrou, NinjaDanz3r, NoooneyDude, NuclearWinter, nuke, Ofek, PerfectTangent, PetMudstone, Puzzlemaker1, Pyrosshade, Ranzarth, Raptorizer, RedlineTriad, ReiderJack, RemberBL, Remo Andreoli, Richard Van Tassel, Robustin, Scorr, Semuca, Shelby Drabant, Skrimble, SluggyWuggies, spacerecycler, Steven Kessler, ThatDan123, THE0BEAST, Tim, Tjarr737, Vlad, vladb, Vladimír Kincl, Vlandemart, wraith-54321, YotaXP, yoysam, Zagamun, Ziiiiiplock

Homepages: unknown-horizons.org, unknownhorizons
Media: Unknown Horizons
Inspiration: Anno (series)
Download: unknown-horizons.org/downloads
Developers: Aaron Franke, Aleksi Kinnunen, Allan Nordhøy, Andre R., Andriy Bandura, Andrzej Bylicki, Antagonym, Armcoon, Arti, avalon3515, Bernhard M. Wiedemann, bringerer, chobkwon, Chris Oelmueller, Christoph Egger, cmocanu, Daniel André Eikeland, David Ulrich, desophos, DSAureli, Elizabeth Sherrock, Emil Hemdal, Fabian Streitel, Ghislain LEVEQUE, GreyGhost, icyvapor, Ivan, J.M. de Jong, Jakub Janek, Jana Weigel, jdigreze, Joan Josep, JOKer, Jorge Maldonado Ventura, Karar Al-Remahy, kennedyshead, Koji, Kornelijus Tvarijanavičius, Krzysztof Nowak, KT, LafarM, LostDaemon, Luis Martinez, Luiz Fernando Ranghetti, Lukáš Krejza, Mantas Kriaučiūnas, Manuel Mausz, Marius Schiffer, Markus Hackspacher, Mayeul Cantan, Mesutcan Kurt, Michael Alexsander, Michal Čihař, Mihai Bivol, milotype, Moritz Beller, Niektory, Nightraven, Nihathrael, nxxs, OlhaQue, Omaranwa, Ott Tinn, PacLow, Pavel, Pedro Henrique, Per Hermansson, Polshakov Dmitry, ptrsk, Ramon, Raphael Isemann, Reiner Gerecke, Robert Mitwicki, Rubén Viguera Marañón, rudis, Rui, Sandra, schtritoff, Sebastian Rasmussen, Siddharth Kothari, Silvério Santos, Slobodan Simić, Szabolcs Tóth, Thomas Kinnen, Thomas Kowaliczek-Schmer, Tobias Schröfel, totycro, totycro uhyi, Translators, ttoocs, Tuomas Lähteenmäki, UnknownScribe, Viktoria S., Vivek, Volkan Gezer, Weblate (bot), Zappaman

Homepages: unnethack.wordpress.com, unnethack
Media: UnNetHack
Inspiration: NetHack
Download: unnethack/files/unnethack
Developers: aaxelb, copperwater, David Haft, Fredrik Ljungdahl, Guanpeng Xu, Guest41, guest41, gurr, Karl Garrison, kdgarris, Mikko Juola, NHTangles, Pasi Kallinen, Patric Mueller, Raz, tedav, Tung Nguyen, xororand

Homepages: unvanquished.net, unvanquished
Media: Unvanquished
Inspiration: Natural Selection
Download: unvanquished.net/download
Developers: Amanieu d'Antras, Anthony J. Bentley, caldazar-at, cmf028, Corentin Wallez, cu-kai, Darren Salt, David CARLIER, DefaultUser, DeLift, Dimitriio, Dmitry Tsarevich, Dolce Triade, gimhael, Gireen, gmcode, hurf blurf, Jani Mäkinen, jaytersen, kharnov, M. Kristall, maek, Mattia Basaglia, Maximilian Stahlberg, Morel Bérenger, necessarily-equal, neumond, Paweł Redman, Sixthly, slipher, Theodoros Theodoridis, Thomas Debesse, Tim, TimePath, Trinitrotoluene-, Veyrdite, Viech, Zachary L, Zack Middleton