Stargate is a multimedia franchise based on the 1994 film of the same name written by Roland Emmerich and Dean Devlin. It centers around the eponymous device, the "stargate", which enables near-instantaneous travel across the universe. The franchise began with the original film, released on October 28, 1994. In 1997, Brad Wright and Jonathan Glassner adapted the film for television and created Stargate SG-1. It was followed by two spin-offs: Stargate Atlantis in 2004 and Stargate Universe in 2009. Additionally, three films and various novels, comics, audio books, and web series were released based on the televisions series. A number of video games were announced and being developed, but were ultimately canceled in various stages of completion.
The original film introduced the "stargate" and applied the ancient astronauts theory to establish that ten thousand years ago a parasitic alien discovered Earth and the primitive humans. The alien enslaved the humans and posed as a god, Ra, using the stargates to transport humans across the galaxy to work as slave labor. Eventually, the humans rebelled and buried the stargate.
In 1928, the stargate was discovered by archaeologist Paul Langford and eventually brought to the United States. During the war, they conducted experiments to try and unlock its secrets, but without success. In the modern day, Langford's daughter Catherine continued his research. In 1994, changed to 1996 in Stargate SG-1, Doctor Daniel Jackson solved the mystery and became part of a team led by Colonel Jack O'Neill to travel to another planet. The planet, Abydos, was inhabited by an Ancient Egyptian civilization, who worshiped Ra. O'Neill and Jackson eventually killed Ra to prevent the destruction of Earth.
Stargate SG-1 established that Ra was a member, and the leader, of a race known as the Goa'uld, who pose as gods to the primitive humans. Ra's death created a power vacuum, which was largely filled by Apophis, the God of Death. A team known as SG-1 was formed, led by Jack O'Neill and consisting of Daniel Jackson, Samantha Carter, and the Jaffa Teal'c. SG-1, and other teams, explored the galaxy to find allies and technology in the fight against the Goa'uld.
As the longest-running series in the franchise, SG-1 introduced many new concepts over the years. New allies and enemies such as the Asgard, Replicators, and Ori, as well as new characters such as Jonas Quinn, Colonel Cameron Mitchell and Vala Mal Doran. It also introduced the Ancients, the race responsible for building and seeding the stargates.
Stargate Atlantis established that the Ancients built the giant city of Atlantis, which they subsequently used to leave the Milky Way galaxy after a plague decimated much of their race. They settled in the Pegasus galaxy where they built a new civilization and seeded human life on many planets. But they eventually encountered the Wraith, a vampire-like race that feed on the life energy of living beings. The Ancients ultimately lost, with eventually only Atlantis remaining.
In 2004, the Atlantis expedition arrived on Atlantis to find Ancient technology, only to be isolated from Earth with no way back. They inadvertently awaken the Wraith after thousands of years of hibernation and alert them to the existence of Earth. Using the technology of the city and by finding new allies, the Expedition fought the Wraith to prevent them from ever finding Earth.
Stargate Universe introduced the Destiny, a very old ship built by the Ancients to investigate the mysterious Cosmic Microwave Background Radiation. The ship was accompanied by seed ships which manufactured stargates and planted them on planets along the ship's route.
The Destiny was discovered by an expedition that sought to unlock the ninth and final chevron of the stargate. After being forced to evacuate their off-world base during an attack, the survivors found themselves billions of light-years from Earth. Universe was much darker in tone than the previous shows, and focused primarily on the interpersonal relationships and the issues that were caused by being lost far from home.