Stargate is a military science fiction media franchise based on the film directed by Roland Emmerich, which he co-wrote with producer Dean Devlin. The franchise is based on the idea of an alien wormhole device that enables nearly instantaneous travel across the cosmos. The franchise began with the film Stargate, released on October 28, 1994, by Metro-Goldwyn-Mayer and Carolco, which grossed US$197 million worldwide. In 1997, Brad Wright and Jonathan Glassner created a television series titled Stargate SG-1 as a sequel to the film. This show was joined by Stargate Atlantis in 2004, Stargate Universe in 2009, and a prequel web series, Stargate Origins, in 2018. Also consistent with the same story are a variety of books, video games and comic books, as well as the direct-to-DVD movies Stargate: Children of the Gods, Stargate: The Ark of Truth, and Stargate: Continuum, which concluded the first television show after 10 seasons.

The mythology of the Stargate franchise is a complex and eclectic fictional backstory, which is presented as being historical, of the Stargate premise. A "rich mythology and world-building" are used to establish "a vast cosmology and an interesting alternate take on the history of Earth"; a defining feature is "its use of ancient mythology, with stories that take inspiration from multiple places around the globe". Narratives center around xeno-mythology as experienced by humans during episodic contact with alien races. Audiences across a variety of platforms - including TV series, novels, comics and movies - witness the people of Earth exploring a fictional universe using the Stargate. Species established early on in the franchise recur throughout, with one adversary often dominating a particular story arc, which can continue across several seasons.