"Stargate is a military science fiction franchise, initially conceived by Roland Emmerich and Dean Devlin. The first film in the franchise was simply titled Stargate. It was originally released on October 28, 1994 by Metro-Goldwyn-Mayer and Carolco, and became a worldwide hit grossing nearly $200 million (USD) worldwide. Three years later, Canadian Brad Wright and Jonathan Glassner created a television series titled Stargate SG-1 as a sequel for the film.
In addition to film and television, the Stargate franchise has expanded into other media, including books, video games, and comic books. These supplements to the film and television series have resulted in significant development of the show's fictional universe and mythology. In 2008, the films Stargate: The Ark of Truth and Continuum were released direct-to-DVD, which in total grossed over $21 million in the United States. In 2002 the franchise's first animated series, Stargate Infinity, began airing, which holds no canonicity in the franchise despite its Stargate SG-1-inspired plot. In 2004, the TV series Stargate Atlantis was released as a spin off from Stargate SG-1 and a third series, Stargate Universe, premiered on October 2, 2009."
Source: Wikipedia, "Stargate franchise", available under the CC-BY-SA License.