Maintains various outposts on several worlds in the Pegasus Galaxy
- "We need to get back out there; do what we came to do."
- —Elizabeth Weir
The Atlantis Expedition is Earth's international mission to the Ancient city of Atlantis in the Pegasus Galaxy. The impetus for the mission was the discovery of the Ancient outpost in Antarctica, which SG-1 used to destroy the attacking fleet of the Goa'uld Anubis. After discovering the location and fate of the abandoned settlement, the Expedition took up residence and began exploring the worlds of this new, unexplored galaxy, forging alliance with native races and steadfastly opposing the dominance of the Wraith.
Following the Wraith attack on Earth, the Expedition was dissolved pending a United Nations review of its mandate and future. A reconnaissance mission back to Pegasus several months later would reveal a startling and disturbing buildup of Wraith forces, however, and the Atlantis Expedition was reinstated and allocated additional funding for its efforts.
- "We are about to evacuate this city in the hope that it will lie safe for many years, and then, one day, our kind will return. And they have."