The third season of the military science fiction television series Stargate SG-1 commenced airing on Showtime in the United States on June 25, 1999, concluded on Sky1 in the United Kingdom on March 8, 2000, and contained 22 episodes. The third continues the plot started in season one, the third season follows SG-1 in their fight against the Goa'uld Empire's System Lords, the main being Sokar until "The Devil You Know" and then Apophis after regaining power after the event in "The Devil You Know." The season introduces the long unseen and unnamed enemy of the Asgards, the Replicators who are self-replicating machines that seek to convert all civilizations into more of themselves, thus posing a dire threat to all other beings. The Replicators are first mentioned, but not named, in season three episode "Fair Game".
The one-hour premiere "Into the Fire", which debuted on June 25, 1999 on Showtime did not receive any syndication rating, but overall got a high viewership level. The series was developed by Brad Wright and Jonathan Glassner, who also served as executive producers. Season 3 regular cast members include Richard Dean Anderson, Michael Shanks, Amanda Tapping, Christopher Judge, and Don S. Davis.
O'Neill, Carter and Jackson must escape Hathor's clutches, while Teal'c tries to raise a Jaffa army on Chulak. General Hammond must take desperate measures to rescue the team.
SG-1 must find a renegade Goa'uld who has been hiding on Earth for thousands of years.
The Asgard aid Earth in negotiating a nonagression treaty with the Goa'uld System Lords.
When Daniel goes insane, SG-1 must deal with the legacy of Machello's anti-Goa'uld technology.
SG-1 discovers a planet where children are used to acquire knowledge for the entire population, then discarded.
SG-1 must free an alternate reality Earth from a Goa'uld invasion after duplicates of Samantha Carter and Charles Kawalsky come through the quantum mirror.
SG-1 is taken captive by an alien bounty hunter with uncertain loyalties.
SG-1 finds a medieval Christian society terrorized by Sokar and the Unas, and is accused of being possessed by demons.
SG-1 discovers a military camp where young men are trained to impersonate SGC personnel to infiltrate Earth.
Jackson deals with the apparent death of his wife, Sha're, at the hands of Teal'c.
SG-1 encounters an entire planet suffering from amnesia. The planet's leader returns to Earth with SG-1 to find a cure, but SG-1 suspects she may not be who she appears to be.
When Major Carter's father Jacob is kidnapped by Sokar, the SG-1 team must infiltrate a prison moon designed to look like hell to rescue him.
SG-1 must escape a hellish prison moon, and one of their worst enemies.
SG-1 returns from a mission and discovers that metamorphic aliens have taken over the complex.
The Tollan put Skaara and Klorel on trial to determine who will control the host body.
SG-1 receives alien brain implants that manifest themselves as a bizarre man, who tells them that they would not survive the procedure to remove him.
After a meteor strike buries the Stargate, O'Neill finds himself stranded on a planet with no hope of rescue.
O'Neill steals technology from the Tollan, and is forced to leave the Stargate program. Maybourne offers an intriguing proposal.
The members of SG-1 are imprisoned on a planet and become pawns in a war of ideology.
SG-1 discovers the mystical planet Kheb, and must find the Harcesis child of Apophis and Sha're before Apophis's army does.
An alien artifact causes Daniel to disappear, and the team looks for help from his institutionalized grandfather.