Tom Clancy's Rainbow Six Siege is an online tactical shooter video game developed by Ubisoft Montreal and published by Ubisoft. It was released worldwide for PlayStation 4, Windows, and Xbox One on December 1, 2015; the game was also released for PlayStation 5 and Xbox Series X/S exactly five years later on December 1, 2020. The title received a port for Google Stadia on June 30, 2021, and one for Amazon Luna in January 2022. The game puts heavy emphasis on environmental destruction and cooperation between players. Each player assumes control of an attacker or a defender in different gameplay modes such as rescuing a hostage, defusing a bomb, and taking control of an objective within a room. The title has no campaign but features a series of short, offline missions called, "situations" that can be played solo. These missions have a loose narrative, focusing on recruits going through training to prepare them for future encounters with the "White Masks", a terrorist group that threatens the safety of the world.

Tactical shooter is a sub-genre of first- and third-person shooters, associated with using strategy, planning, and tactics in gameplay, as well as the realistic simulations of ballistics, firearm mechanics, physics, stamina, and low time to kill. Dating back to strategy games from the late 1980s, the genre first rose to prominence in the late 1990s with the releases of several well-received tactical shooters. The popularity of the genre saw a decline in the late 2000s as fast-paced "arcade"-like action shooters rose to prominence, it has seen a revitalization since the mid-2010s with the successful releases of several modern tactical shooters.