X-COM: Alliance is a cancelled video game in the X-COM series. The game was developed by two different teams of MicroProse developers (first as a subsidiary of Spectrum Holobyte, then Hasbro Interactive, and finally Infogrames Entertainment) between 1995 and 2002. It had the player assume the role of commander of the militarized scientific mission lost in space during the aftermath of X-COM: Terror from the Deep.

Unlike other games in the X-COM series, most of which were strategy games, Alliance was a first-person shooter. It was described as having strategy, adventure, and role-playing elements. After being officially announced in 1998 for a planned release in the first half of 1999, the game was repeatedly delayed and put on hold, before eventually becoming vaporware; it was eventually cancelled in 2002. Since then, it had numerous build versions leaked online.