This is a list of recurring alien characters in the science fiction television series Stargate SG-1.
The Abydonians are the people whom Colonel O'Neill's team encounters on another planet in the Stargate film. They are the slaves of the alien Ra and are descendants from ancient Egyptians brought through the Stargate to mine the fictional mineral naqahdah. The film gives the location of their homeworld—named Abydos in SG-1's pilot episode "Children of the Gods"—as the Kaliem galaxy "on the far side of the known universe" (a vague reference to the constellation Caelum, perhaps) in the film; and as the closest planets to Earth in the Stargate network in "Children of the Gods". In the film, O'Neill and Daniel Jackson inspire the Abydonians and their leader, Kasuf, to rise up against Ra. The military personnel return to Earth, while Daniel falls in love with Kasuf's daughter Sha're and remains behind. In "Children of the Gods", set a year after the film, the Goa'uld Apophis attacks Abydos, abducting Sha're and her brother Skaara to serve as hosts for his queen Amonet and son Klorel. In season 6's "Full Circle", the Goa'uld Anubis destroys Abydos, but Oma Desala helps its entire population Ascend.
The Ancients are the original builders of the Stargate network, who by the time of Stargate SG-1 have ascended beyond corporeal form into a higher plane of existence. The humans of Earth are the "second evolution" of the Ancients. The Ancients (originally known as the Alterans) colonized the Milky Way galaxy millions of years ago and built a great empire. They also colonized the Pegasus galaxy and seeded human life there before being driven out by the Wraith. The civilization of the Ancients in the Milky Way was decimated thousands of years ago by a plague and those who did not learn to ascend died out. With few exceptions the ascended Ancients respect free will and refuse to interfere in the affairs of the material galaxy. However their legacy is felt profoundly throughout the Stargate universe, from their technologies such as Stargates and Atlantis to the Ancient Technology Activation gene that they introduced into the human genome through interbreeding.