Star Trek: The Original Series contains an impressive 29 episodes in season 1, significantly more than most modern television series. So while TOS only ran for three seasons, it delivered 79 total episodes, some of which hold up better than others. In its first season, Star Trek: The Original Series laid the groundwork for everything that came after, establishing a fictional universe that remains relevant and popular today. Some of Star Trek's best moments come from season one, from the introduction of the Klingons and the Romulans to one of Kirk's greatest romances.
10 "A Taste Of Armageddon"
Star Trek: The Original Series Season 1, Episode 23
The USS Enterprise visits the planet Eminiar VII and discovers a society that is fighting a computer-simulated war with a neighboring planet. When the Starship Enterprise is "destroyed" in a simulated attack, the planet's leaders expect Captain Kirk and his crew to turn themselves over for execution. Ultimately, Kirk destroys the computers that simulate the war, forcing the two sides to either fight a real war or negotiate for peace.
"A Taste Of Armageddon" is an underrated episode about the futility of war that may be even more relevant today than it was in the 1960s.
9 "The Menagerie"
Star Trek: The Original Series Season 1, Episodes 10 & 11
Star Trek: The Original Series' only two-part episode reuses footage from Star Trek's original unaired pilot, "The Cage," to introduce audiences to Captain Christopher Pike (Jeffrey Hunter). Spock as risks his life and career to help his former captain, after Pike suffered a terrible accident that left him paralyzed and barely able to communicate. Spock plans to bring Pike to Talos IV, where the powerful Talosians can create realistic illusions for Pike to live out the rest of his life.
Anson Mount's Captain Pike learned of his tragic fate in Star Trek: Discovery season 2, and he struggles with the knowledge throughout Star Trek: Strange New Worlds.
8 "Errand Of Mercy"
Star Trek: The Original Series Season 1, Episode 26
"Errand of Mercy" is known for introducing the Klingons, and it's a solid episode in its own right. When Captain Kirk and Spock attempt to persuade the Organians to resist Klingon occupation, the Organians refuse to get involved. A contingent of Klingons soon arrive, led by Commander Kor (John Colicos), and take over Organia with no resistance. The Organians eventually reveal themselves to be powerful non-corporeal beings, and they single-handedly put an end to the Federation/Klingon war.
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7 "Space Seed"
Star Trek: The Original Series Season 1, Episode 22
When the Starship Enterprise finds the SS Botany Bay drifting in space, they discover a group of cryogenically frozen augmented humans from Earth's history. Among these Augments is Khan Noonien Singh (Ricardo Montalbán), who was once a tyrant responsible for conquering nearly one-quarter of Earth's population. In "Space Seed," Khan takes over the Enterprise, with help from historian Lt. Marla McGivers (Madlyn Rhue), and Kirk later maroons Khan and his people on the planet Ceti Alpha V.
An all-new scripted audio series entitled Star Trek: Khan is set to premiere later in 2025, and will explore Khan's life on Ceti Alpha V. Lost alum Naveen Andrews provides the voice for Khan and For All Mankind's Wrenn Schmidt voices Lt. McGivers.
Khan was one of the most cunning villains Kirk faced on Star Trek: The Original Series, and Ricardo Montalbán makes him impossible to forget. Although "Space Seed" sets up one of the best Star Trek movies in Star Trek II: The Wrath of Khan, the episode also stands on its own as a compelling hour of television. Lt. McGivers may develop an attraction to Khan a bit too quickly, but she comes around in the end, and everything else about the episode works.
Star Trek: The Original Series Season 1, Episode 25
When the Enterprise visits a mining facility to investigate a series of deaths, they encounter a silicon-based lifeform living in the caves. Eventually, Spock initiates a mind meld with the creature and learns that it is called the Horta. The Horta has simply been protecting its eggs, which the miners have unknowingly been destroying. Dr. McCoy treats the Horta's wounds, and Kirk explains the situation to the miners.
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"The Devil in the Dark" is a quintessential episode of Star Trek and a celebration of diversity and life in all of its forms. Despite the losses suffered on both sides, the miners and the Horta agree to live alongside one another in the end, a message that remains just as relevant and necessary as ever. Spock's mind meld with the Horta is beautifully played by Leonard Nimoy, and the episode is a great exploration of Kirk and Spock's friendship.
5 "Arena"
Star Trek: The Original Series Season 1, Episode 18
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Captain Kirk's fight with the Gorn remains one of his most memorable moments, and "Arena" has many of the elements that make Star Trek great. The episode feels like classic science fiction at its best, as Kirk uses his ingenuity to stay alive on a strange alien landscape. Ultimately, it's Kirk's decision to be merciful that saves him and his ship, which perfectly exemplifies Star Trek's philosophy.
4 "The Corbomite Maneuver"
Star Trek: The Original Series Season 1, Episode 10
"The Corbomite Maneuver" was the first regular episode of TOS filmed after the two pilots, but aired as the tenth episode, due to the more complex special effects.
In the end, Kirk's bluff works and the real Balok (Clint Howard) reveals himself as a small child-like alien who was only testing the Enterprise and its crew. "The Corbomite Maneuver" remains an incredibly compelling episode of television and illustrates that Kirk can be clever in addition to being a good strategist and capable fighter. The episode keeps things interesting until the very end, and concludes with a hopeful note that feels perfect for Star Trek.
3 "The Galileo Seven"
Star Trek: The Original Series Season 1, Episode 16
"The Galileo Seven" shifts the focus to Spock, following the Vulcan Science Officer as he leads an ill-fated away mission. When their shuttlecraft is pulled off course, Spock is forced to make an emergency landing on a rocky planet. The giant ape-like creatures who live on the planet soon attack the landing party, killing one of the officers. Spock faces one complication after another, including an insubordinate officer, and he struggles with the idea that logic cannot solve every problem.
Spock and Chief Engineer Scotty (James Doohan) eventually repair the shuttle, and Spock trusts his instincts, dumping the shuttle fuel and igniting it like a signal flare. As a fan of Spock, "The Galileo Seven" remains one of my favorite Star Trek episodes, and it marks an important step on Spock's journey to learn that "logic is the beginning of wisdom, not the end."
2 "Balance Of Terror"
Star Trek: The Original Series Season 1, Episode
In one of the most tense episodes of Star Trek, Captain Kirk and the Enterprise get caught in a cat-and-mouse game with a Romulan Bird-of-Prey. The Romulan Commander (Mark Lenard) proves to be a match for Kirk when it comes to strategy, and the battle keeps everyone involved on their toes. Kirk emerges as the victor in the end, but his ship loses a crew member and the Federation only just avoids another war with the Romulans.
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1 "The City On The Edge Of Forever"
Star Trek: The Original Series Season 1, Episode 28
No list of great Star Trek episodes is complete without "The City on the Edge of Forever," and with good reason. Harlan Ellison's story follows Kirk and Spock, as they travel back in time to retrieve Dr. McCoy and correct the changes he inadvertently caused in the timeline. Kirk falls in love with a soup kitchen operator named Edith Keeler (Joan Collins), only to learn that she has to die to restore the proper future.
"The City on the Edge of Forever" remains one of Star Trek's most beautifully tragic stories, and a pitch perfect episode of Star Trek: The Original Series.
