- Home: https://openxcom.org/
- Media: https://en.wikipedia.org/wiki/UFO:_Enemy_Unknown#Fan-created_content
- Inspiration: X-COM: Apocalypse, X-COM: Terror from the Deep, X-COM: UFO Defense
- State: mature
- Download: https://openxcom.org/downloads-milestones/
- Keyword: remake, strategy, turn-based
- Code repository: https://github.com/OpenXcom/OpenXcom.git (@created 2011, @stars 1580, @forks 422)
- Code language: C++
- Code license: GPL-3.0
- Developer: 54x, Alexander Kashev, Alexey Rogachevskiy, alienfood, Andrew Schultz, Andriy B. Kmit', Andriy Kmit', Andrzej Owsiejczuk, Angelos Tzotsos, atlimit8, Azamat H. Hackimov, boozedog, cfailde, cornels, d2uriel, Daniel, DarkDefender, Dmitriy Trushnikov, Dmitry Marakasov, dtrushn, Eino Keskitalo, FalkoOXC, Fenyő, Gix, greg, Greg Bonik, Greg V., Guido Pinkas, hackbunny, IvanDogovich, Jaco, Jason Gilbert, Jay Atkinson, JDarthenay, Jonathan Hamilton, kevL, Kim Nilsson, Konstantinos Arvanitis, Krzysztof Knapik, Marq Watkin, Meridian, Myk, NHOrus, Nik Konyuchenko, nilekurt, OmniscientQ, Player701, R1dO, radius75, redv, Ross Horsman, Ryan C. Creasey, ShadowGJ, sheepo99, Shugyousha, stefkosdev, stiiin, tomvd, Tomáš Chvátal, uqs, Volutar, Warboy1982, Westin Breger, WorMzy Tykashi, Yankes, ZehCastro
OpenXcom requires a vanilla version of the original UFO: Enemy Unknown / X-COM: UFO Defense (any edition) with the latest patch.
- Build system: CMake