26 episodesFirst aired 14 September 1967
E1Sept 196750m
First Officer Spock returns to his home world for a brutal Vulcan mating ritual.
E2Sept 196751m
The crew of the Enterprise are held captive by an alien who turns out to be the Greek god Apollo.
E3Sept 196750m
The crew of the USS Enterprise deals with an indestructible planet-destroying space probe.
E4Oct 196750m
A transporter mishap swaps Captain Kirk and his companions with their evil counterparts in a parallel universe. In the so-called Mirror Universe, the Enterprise is a ship of the Terran Empire, an organization as evil as the United Federation of Planets is benevolent.
E5Oct 196750m
The crew of the Enterprise visits a mysterious paradisical planet controlled by a computer that is served by the local inhabitants.
E6Oct 196751m
The starship Enterprise and its heavily-damaged sister ship, the USS Constellation, must work together to stop an alien planet-killing machine headed for the heart of Federation territory.
E7Oct 196750m
Two powerful aliens threaten the well-being of the Enterprise and her crew.
E8Nov 196751m
Captain Kirk has a second run-in with the conman, Harry Mudd. Mudd is now the supreme ruler of a planet of androids who cater to his every whim.
E9Nov 196750m
A shuttle crew from the USS Enterprise encounters a man out of history and his mysterious alien companion.
E10Nov 196750m
The Enterprise must transport dignitaries to a peace conference, with an assassin on the loose.
E11Dec 196750m
The crew of the Enterprise become entangled in a planet's tribal power struggle.
E12Dec 196750m
Strange radiation exposes the command crew of the Enterprise to the effects of rapid aging.
E13Dec 196750m
Captain James T. Kirk becomes obsessed with destroying a deadly entity he once encountered in his youth.
E14Dec 196751m
A series of bizarre murders points to Mr. Scott as the prime suspect.
E15Dec 196750m
The Enterprise must protect a very important shipment of grain from both Klingons and some adorable creatures called tribbles.
E16Jan 196850m
Captain Kirk and his companions are abducted into slavery and trained to fight as gladiators for the gambling entertainment of three disembodied beings.
E17Jan 196850m
The Enterprise visits a planet with an Earth-like 1920s gangster culture.
E18Jan 196850m
The crew of the Enterprise encounters an energy-draining field which may be able to destroy the galaxy.
E19Feb 196851m
The crew of the Enterprise discovers Klingon interference in the development of a formerly peaceful planet and is forced to help maintain a balance of power.
E20Feb 196850m
Ancient alien minds are given control of Captain Kirk's and First Officer Spock's bodies.
E21Feb 196850m
The crew of the Enterprise tracks down a Federation observer on a planet dominated by a "Naziesque" regime.
E22Feb 196850m
Beings from another galaxy commandeer the Enterprise in an attempt to return home.
E23Mar 196850m
Captain Kirk must find the cure to a deadly disease and put an end to another Starfleet captain's cultural interference.
E24Mar 196850m
A skeleton Enterprise crew are assigned to test a revolutionary computer system that is given total control of the ship.
E25Mar 196850m
The Enterprise crew investigates the disappearance of a ship's crew on a planet that is a modern version of the Roman Empire.
E26Mar 196850m
While back in time observing Earth in 1968, the Enterprise crew encounters the mysterious Gary Seven who has his own agenda on the planet.