Founding commanding officer of SG-1. Joining the Air Force at 18, O'Neill proved himself to be an exceptional and gifted airman and was later assigned to a Special Forces unit. He resigned from the military when his son, Charlie, died by accidentally shooting himself with O'Neill's service weapon. O'Neill was devastated by the loss, which eventually drove his wife to divorce him. He was later recalled to duty by his former commanding officer and sent through the Earth's first discovered Stargate, in a mission that gave him a new desire to live. After several years of leading SG-1 through missions across the galaxy, helping to save Earth innumerable times, he was promoted to Brigadier General and chief of Stargate Command. Most recently, he was appointed by President Hayes to serve as the head of the newly created federal department of Homeworld Security and promoted to the rank of major general.

A veteran of the first exploratory team from the movie Stargate, Dr. Daniel Jackson is an anthropologist and linguist and an expert in ancient and current cultures; he speaks over 20 languages, including ancient Egyptian. He had originally been contracted by the military to decipher a mysterious hieroglyphic cartouche. His subsequent translation of it allowed the Earth's first discovered Stargate to be opened. As a member of SG-1, Dr. Jackson's humanistic approach was often in conflict with Colonel Jack O'Neill's militaristic style.

Some saw Dr. Jackson as a soft, brainy, clumsy scientist who carried a wide-eyed enthusiasm with him through every mission, but he earned the heartfelt trust and respect of O'Neill and all the others - never more so than after sacrificing his worldly existence to save millions of lives in Kelowna, a country on the planet designated P9Y-4C3. He ascended to a higher spiritual plane in place of death. Even before this, he had been considered like a deity to the people of Abydos, the planet on which he'd chosen to stay following that first SG mission. Later banished from Ascension, with no memory of the experience, he returned to human form and rejoined SG-1.

Specialist in Stargate technology, with a doctorate in astrophysics, she brings both extensive scientific knowledge and military training to the SG-1 team. When one of the earliest Stargate-research projects was ended before completion and she was transferred to another base, she continued her research in private before eventually being recruited for SG-1. During her SG-1 tenure, Carter has been promoted from Captain to Major to Lieutenant Colonel and later to Colonel.

Alien of the species known as Jaffa. The Jaffa each carry an infant symbiote in a belly pouch. This symbiote is the larval stage of a separate, parasitic species, the Goa'uld, who use lifeforms from around the galaxy as host bodies. There is a strong symbiotic relationship between the larva and the Jaffa, because the symbiote guarantees its host long life and immunity to disease. Teal'c, however, recently managed to divest himself of his symbiote, and must now depend on the drug tretonin - a distillate of Goa'uld symbiotes - to live. Teal'c - who followed his mentor, Bratac, as First Prime of the notorious Serpent Guards of Goa'uld system lord Apophis - was forced to leave his son Ry'ac and his now-deceased wife Drey'auc behind when he joined SG-1. He hopes to defeat the Goa'uld, and seeks personal redemption for some of his past deeds.

Lt. Col. Cameron Mitchell is a gifted fighter pilot who was seriously injured while saving SG-1 in Season 7's two-part finale "The Lost City." Fully recuperated, Mitchell arrives at Stargate Command to join the team he fought so hard to save, only to find that SG-1 isn't quite like he remembered.

Gen. Hank Landry has been brought out of retirement to replace his longtime friend Jack O'Neill as the new head of Stargate Command.

Founding commander of Stargate Command and all SG units. A hardened military leader and a wise man willing to do whatever is necessary to defend the interests of his country and humanity, he was promoted to a Pentagon position as chief of defense for Earth - a post referred to colloquially as "Head of Homeworld Security."

Complicating the galactic balance of power after the fall of the Replicators is Gerak, a Jaffa leader who competes with Teal'c for political control of the newly emerging Jaffa nation. Most recently, Gerak has given himself to the Ori claiming that everything the Jaffa believe is contained in the Book of Origin. For his loyalty, Gerak was turned into a Prior by the Ori but was later convinced of his mistake and destroyed himself.

Vala is a former goa'uld host who was a scheming, unscrupulous, thieving con artist. In addition to her mysterious agenda, she appears to have a more than passing amorous interest in Dr. Daniel Jackson. Recently she has joined SG-1 in the fight against the Ori.

A scientist and dignitary from Kelowna, one of three nations on the planet Langara (original Earth designation: P9Y-4C3). Quinn was present at the accident that gave Dr. Daniel Jackson a fatal dose of radiation poisoning. Initially involved in a cover-up, Quinn later made amends by smuggling to Earth a small amount of the unstable yet powerful element Naquadria - a derivative of Naqaudah - for SGC to study in the hopes of developing shared defense technology. For his actions, his homeland initially branded Quinn a traitor. Quinn, who has metahuman capacity for absorbing knowledge, replaced the ascended Dr. Jackson on the SG-1 team. With changes in the political winds, however, his homeland and birthright called him back. His former teammates joined him afterward on a mission to save his planet from nuclear destruction.

Military doctor hand-picked for Stargate Command by General Hammond for her wide range of expertise. Dr. Fraiser's skill and compassion enabled her to face the most peculiar cases brought to her by the SG teams. She was killed in the line of duty while tending to a wounded airman on planet P3X-666.