Star Trek Guide

Star Trek: The 10 Best Episodes Of The Original Series To Rewatch, Ranked

As fans are rejoicing about currently having two Star Trek series in production at the same time, they might consider returning to the impetus of Gene Roddenberry's vision of the future in Star Trek: The Original Series. So much of the material that makes up the foundation of Star Trek lore, foundation, and canon comes from the '60s sci-fi classic, with plot points and storylines strongly felt in Star Trek: Picard and to an even greater extent in Star Trek: Discovery.

The five-year mission of Captain Kirk, Mr. Spock, Doc McCoy, and the rest of the crew of the starship Enterprise was full of everything from ethical questions regarding the humanity of artificial intelligence, to political intrigue pitting the Federation against Romulan insurgents. It also introduced fan favorites, from the Vulcan salute to the Mirror Universe. Boldly go where you've already gone before with these 10 classic episodes of Star Trek: The Original Series.


After a transporter accident, Captain Kirk is split into two different entities, a plot point which would be revisited in Star Trek: The Next Generation and Star Trek: Voyager. The episode becomes a study of the captain of the Enterprise, as each personality attempts to assert dominance over the Federation flagship.

One personality is domineering and hostile, while the other is incredibly passive. As the storyline progresses, it becomes something of a morality play, as it becomes increasingly clear that as each Kirk becomes his own man, it becomes a difficult task to determine who has the "right" to remain as the true James Tiberius Kirk.


There's a mystery aboard the Enterprise in "Journey to Babel", which marked the first time that representatives of the Federation's founding members were all together again on screen. Vulcans, Humans, Andorians, and Tellarites all appear to attend the Babel Conference, and later a murder occurs.

Not only is the episode full of classic Trek humor, intrigue, and galactic politics, it also reveals a lot about Spock's upbringing. His Vulcan father and human mother are also included in the mix, and Spock undergoes a great deal of character development thanks to the familial exchanges between them.


With many Star Trek series like Star Trek: The Next Generation, Star Trek: Discovery, and even Star Trek: Picard piggy-backing so many episodes of the original series with their plots and storylines, it's important to remember that what made it unique sometimes came down to Captain Kirk's captaincy.

In "The Corbomite Maneuver", the Enterprise encounters a mysterious alien intent on attacking it. Thanks to Kirk's quick thinking, he outmaneuvers its assault. The episode provides great insight into Kirk's tactical skill, and the original series' ability to create tension without the fancy visuals of Star Trek: Discoverythough we suspect Captain Lorca would approve of Kirk's plan.


Not only did "Balance of Terror" introduce the nefarious Romulans to Star Trek canon, but it also featured a pragmatic battle of wills between warriors that, as one Romulan commander relays so poignantly to Captain Kirk, could have been friends in another reality. It reminds viewers that neither men are good nor evil, simply men on missions.

Though the Federation had fought the Romulans 100 years prior, until the incident along the neutral zone that opens the episode, no Federation starships had engaged a Romulan vessel in the years since, making this the premier occasion for visual contact.


In one of the most harrowing episodes in Star Trek franchise history, a destructive machine goes out of control, sparking the sort of paranoia and fear that existed during the Cold War happening during the show's broadcast. Known as the Doomsday Machine, it's being hunted by Captain Kirk and Commander Decker in an attempt to prevent it from destroying entire planets.

While Kirk sees finding the location of the device one of many missions he needs to complete in the Enterprise's five-year journey, Decker becomes increasingly obsessed. As Kirk nevertheless faces off against it, he continues to promote a message of peace despite the terrifying alternative.


This episode was highlighted by two major components of Trek branding - a memorable nemesis, and the presence of relentless optimism. Ricardo Montalban introduced one of the most iconic villains in the entire Star Trek franchise as Khan Noonien Singh, a former dictator of Asia in the wake of the 20th century Eugenics War.

Khan represented the lowest point of humanity and Earth, while Captain Kirk and Co. stood for the great strides that it would come to make between the 20th and 24th centuries. It's not only necessary Trek to view, but sows the seeds of a great rivalry in Star Trek II: The Wrath of Khan.


Though The Federation may have outlawed cloaking technology by the time Star Trek: The Next Generation was on the air, in Star Trek: The Original Series, it was very much favored. The Federation went so far as to send Kirk and Spock aboard a Romulan vessel to obtain the details of its engineering.

This premise has been visited again in Season 1 of Star Trek: Discovery, with Klingons in place of Romulans, but a similarly bizarre romantic interlude occurs. In "The Enterprise Incident", Spock participates in an uncharacteristically malevolent seduction of a female Romulan for the sake of the mission, adding complexity and depth to his character.


The first appearance of pon farr in Star Trek history occurs in this memorable episode when Mr. Spock's ordinarily reserved equipoise is disrupted by the Vulcan mating ritual. The Enterprise is rerouted to Vulcan so Spock can take care of his needs with a pre-arranged partner, only to find that she prefers another mate.

Not only does the episode provide insight into Vulcan life, but it also reveals another side to Spock and Kirk's friendship. Not even a fight to the death can drive a wedge between the two, though it's great fun seeing the ordinarily calm and collected Spock lose his cool Vulcan facade. It's also the premiere of the Vulcan salute!


In one of the most revered episodes in Star Trek canon, one of the most difficult questions in sci-fi is posed; should one person be allowed to die, if their death would keep history intact and save millions? The query is raised when Captain Kirk and Mr. Spock travel back in time to save a raving Doc McCoy, ending up in 1930's America.

The episode is important for not only setting a precedent for time-travel stories in future Star Trek episodes but also to demonstrate that Captain Kirk was capable of true love and William Shatner of genuine acting. Kirk's sacrifice of a future with Edith Keeler so that the future of Earth remains secure is one of the most profound ethical quandaries in the entire franchise.


Before this episode's plot became a huge story arc in Star Trek: Discovery, it captured the imagination of fans everywhere as they watched the usually sterling crew of the Enterprise be depicted as malicious conquerors in an alternate reality. A transporter incident sends Kirk and Co. to a parallel universe, where the only opportunity for advancement on a starship is through assassination.

In this "Mirrorverse", The Federation has been replaced by a Klingon-type organization called the Terran Empire. Captain Kirk behaves with the sort of brutal malevolence only glimpsed at in "The Enemy Within", and even a heavily scarred Sulu becomes a vengeful officer, in a reality where everyone is the polar opposite of Federation ideals.