Thief is a series of stealth video games in which the player takes the role of Garrett, a master thief in a fantasy steampunk world resembling a cross between the Late Middle Ages and the Victorian era, with more advanced technologies interspersed.

The series consists of Thief: The Dark Project (1998), Thief II: The Metal Age (2000), Thief: Deadly Shadows (2004) and Thief (2014). An expanded version of Thief: The Dark Project, titled Thief Gold, was released in 1999 and features three extra maps and a number of bug fixes. Looking Glass Studios developed both The Dark Project and The Metal Age. After the studio had gone out of business in 2000, many former employees moved to Ion Storm and began developing the third part of the series, Deadly Shadows. Eidos Montréal was subsequently given the reins for Thief. The Thief series has been highly acclaimed by both gamers and critics, with praise aimed at the innovative gameplay, atmosphere, sound design, the refreshingly dark and mature tone and direction, distinctiveness from other video games at the time of its release, voice acting and storylines, with the series now being as a pioneer of the modern-day stealth game genre, serving as a major influence to numerous other video games in the stealth genre.