UFO: Enemy Unknown

UFO: Enemy Unknown (X-Com: UFO Defense in USA) is a popular strategy videogame made by Mythos / Microprose, where you take control of the X-Com organization to fight off the alien menace invading Earth.

Minimum system requirements: 

UFO: Enemy Unknown data files and the OpenXcom engine:http://lgdb.org/engine/openxcom

External links:
Developer: Mythos Games, MicroProse