Col. Samantha Carter
Amanda Tapping
Brilliant and beautiful Air Force Colonel Samantha Carter has been reassigned from SG-1 to the city of Atlantis to oversee its operations in the Pegasus Galaxy. Her extraordinary abilities in astrophysics and Gate technology, and her years of combat experience as a member of the elite SG-1, provide the Atlantis team with unmatched military backup.
Lt. Col. John Sheppard
Joe Flanigan
Gifted pilot Lt. Colonel John Sheppard is the military leader of the premiere Stargate Atlantis team. A cunning soldier with a wry wit and wicked golf swing, Sheppard leads the team through both on-base and off-world missions. Season four puts Sheppard’s leadership and bravery to full use as the crew works to stay one step ahead of their longtime foe, the Wraith, and newly emerging enemies sure to test their stamina.

Doctor Rodney McKay
David Hewlett
Dr. Rodney McKay is a brilliant astrophysicist and the chief scientific advisor for the Atlantis Expedition. Though his arrogant and acerbic personality often proves irksome to the other members of the team, his lightning-quick mental reflexes have saved the Atlantis expedition on more than one occasion.

Teyla Emmagan
Rachel Luttrell
The leader of a now primitive but once technologically advanced community on the planet Athos in the Pegasus galaxy, Teyla Emmagan befriends the Stargate Atlantis Expedition and serves as their alien liaison. With her rare ability to sense the Wraith's presence, she is an invaluable ally in the fight against the Atlantis Expedition's primary enemy.

 

Ronon Dex
Jason Momoa
A human native of the Pegasus galaxy — has a physical presence to be reckoned with. Though he is now a trusted member of the Atlantis team, his "kill first, don't bother asking questions" approach to interstellar negotiations brings an explosive element to the team and their often volatile off-world excursions. Before he joined forces with the Atlantis Expedition, Dex fought the Wraith in defense of his planet. He was captured, tortured and then released to become a "runner," the target of a Wraith hunting ritual. That trauma, though firmly behind him, continues to haunt him in subtle ways.

Dr. Jennifer Keller
Jewel Straite
Jennifer Keller is the newest member of the Atlantis expedition, taking over the position of Chief of Medicine. Quietly confident, Dr. Keller must quickly learn how to fit in to the strange and exciting world of Atlantis, and has her medical skills and courage tested early on.
Dr. Carson Beckett
Paul McGillion
Dr. Carson Beckett is the Atlantis team's chief medical doctor. The lovable Scottish physician has a witty sense of humor and his ability to activate Ancient technology frequently lands him in compromising situations. He is credited with discovering the Ancient Gene in humans.
Dr. Elizabeth Weir
Torri Higginson
Attractive, brilliant, but not one to seek the spotlight, Dr. Weir has worked behind the scenes in the U.S. government for several years. Though she's not the one who signs treaties, she has brokered a dozen of the most sensitive international accords in modern history. She has two Ph.D.s, teaches political science at Georgetown University, has served in embassies all over the world and speaks five languages. Though she began her career as a political activist lobbying against government spending on the military, she later decided the best way to stop weapons proliferation was to end the need for them. Placed in charge of Stargate Command by President Henry Hayes, she now commands the Stargate Atlantis team.

Radek Zelenka
David Nykl
A brilliant scientist who hails from the Czech Republic, is an expert on Ancient Technology and most especially the Puddle Jumpers. Even though he's constantly feuding with Rodney McKay, they make an exceptional scientific team when it comes to solving the problems of Atlantis.
Major Lorne
Kavan Smith
Major Lorne first appeared as the executive officer for the mining of Naquadah on P3X-403. He was later transferred to the Atlantis Expedition and has become a very valued member of the Atlantis expedition.

Col. Steven Caldwell
Mitch Pileggi
Col. Steven Caldwell is attached to Team Atlantis as the commander of the intergalactic battle cruiser Daedalus.
Lt. Aiden Ford
Rainbow Sun Francks
The boyishly good-looking young officer once served as the Stargate Atlantis team's military second-in-command. He has since gone rogue, and utilizes a number of unethical and unorthodox strategies in his guerilla war against the Wraith.

Wraith
A hive based society that survives by sucking the life-force from victims thru vampire like suckers in their hands. The Wraith dominate the Pegasus Galaxy, having driven the Ancients from Atlantis thousands of years ago. Awoken from hibernation accidently by the Atlantis team, they now plague Atlantis in their drive to feed and survive in addition to finding a way to Earth for a new feeding ground.