A secret group of scientists have discovered the location of the famous lost city of Atlantis, but it's not on Earth. It's located in another galaxy altogether, the Pegasus galaxy. Stargate Atlantis, a spin-off from the highly successful Stargate SG-1 series, follows a multinational scientific and military group, lead by Diplomat Dr. Elizabeth Weir (played by actress Torri Higginson), headed on a one way trip to Atlantis. Their mission: to investigate the secrets of Atlantis, a city now known to have been built by ancient powerful beings, and bring whatever they discover back to Earth. They will be all on their own, with no means to return, with no means of rescue or support, unless they can find the technology they need in Atlantis to return them to Earth.

Once in Atlantis, the group finds the city abandoned; asleep for tens of thousands of years, and no power source left for a return home. They must find a power source within Atlantis' own Pegasus galaxy using the same Stargate system that got them there or they will be stranded forever. On the first planet they visit, they accidentally waken a new, powerful, and more evil enemy than human kind has ever faced, the Wraith. And the Wraith are hungry - for humans!

Follow the extraordinary adventures of an SGA team lead by Major John Sheppard (played by actor Joe Flanigan), and his team made up by his second in command Lt. Aiden Ford (played by actor Rainbow Sun Francks), and the Astrophysicist/Scientist Dr. Rodney McKay (played by actor David Hewlett, reprising the role he played in Stargate SG-1). Joining the team will be Teyla Emmagan (played by actress Rachel Luttrell), a beautiful, exotic, and strong-willed woman from the Pegasus galaxy.