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The 20 Best Episodes of ‘Star Trek: The Original Series’

A timeless list of thrilling Star Trek episodes that delight, excite, and entertain while exploring the deepest aspects of the human condition and questioning our place in the universe.

Over 50 years have passed since Star Trek debuted its pilot episode “The Cage” on NBC in 1966. Since then, it has become a cultural touchstone for people around the world. With more than a dozen feature films under its belt and a new series currently airing on CBS: All Access, Star Trek: Discovery, the franchise shows no sign of slowing down any time soon.

Featuring classic science fiction camp, drama, and adventure, and a cast of legendary characters including the brash Captain James T. Kirk (William Shatner), the logical Vulcan science officer Spock (Leonard Nimoy), and the passionate Dr. Leonard “Bones” McCoy (DeForest Kelley),
Star Trek: The Original Series makes a strong case for being the most influential science fiction series of all time.

It all began with Gene Roddenberry’s iconic brainchild Star Trek: The Original Series, a series following the crew of the starship Enterprise as it journeys across the vastness of space in the 23rd century. Although the show’s final season suffered from an undesirable time slot and extreme budget cuts, the best episodes of the series rightfully earn their spots among the finest hours in television history. Below is a timeless list of thrilling entries that delight, excite, and entertain, all the while exploring the deepest aspects of the human condition and questioning our place in the universe.

20. “The Doomsday Machine”


“Vulcans never bluff.” – Spock

After receiving a garbled distress signal that could be a starship’s disaster beacon, the U.S.S. Enterprise enters a solar system of decimated planets. Entering a nearby system, they find the same level of destruction and the Enterprise’s sister ship: the U.S.S. Constellation, now derelict and commanded by its sole survivor, the prickly Commodore Matt Decker (William Windom). The crew of the Constellation witnessed the destruction of planets by something “right out of hell”, as Decker grimly puts it: A gigantic planet killer has been unleashed, an automated weapon designed to digest planetary debris for fuel.

Driven by Sol Kaplan’s sonorous score, “The Doomsday Machine” is a suspenseful thriller of an episode. There are distinct echoes of Melville’s Ahab in the traumatized Commodore Decker’s irrational and obsessive pursuit of the planet killer. There is also the shadow of survivor’s guilt. “The commander is responsible for the lives of his crew, and for their deaths,” Decker muses. “Well, I should have died with mine.” When the deadly device begins pulling the Enterprise into its tractor beam, matters become especially dire. Kirk’s plan to destroy the planet killer using a delayed detonation H-bomb device represents everything we have come to know and love about our reckless captain. Strong character development and effective pacing combine in this riveting episode of Star Trek.

19. “Let That Be Your Last Battlefield”


“This will be your final battlefield” – Kirk

When the U.S.S. Enterprise intercepts a stolen Federation shuttlecraft while on a mission to decontaminate a planet plagued by deadly bacteria, a humanoid named Lokai (Lou Antonio) seeking asylum from the war-torn planet Charon is brought aboard. Lokai happens to be split down the middle: black on one side, white on the other. Soon, a similar being shows up from Charon named Bele (Frank Gorshin) who claims to be an officer sent to arrest political traitors. It becomes apparent that Bele and Lokai despise each other because of their racial difference. Tensions over their opposite skin colors drive Bele and Lokai into a war of attrition aboard the ship. In a suspenseful scene with several close-up shots, Bele takes control of the ship while a frustrated Kirk initiates the Enterprise’s auto-destruct sequence (later initiated in Star Trek III: The Search for Spock).

Star Trek delivers a powerful message about racial prejudice in this episode that still resonates with viewers today. A strong performance from guest actor Frank Gorshin, best known for his portrayal of the Riddler in the Batman live-action series, truly elevates the episode. Notably, “Let That Be Your Last Battlefield” ends on a bitter note: Bele and Lokai beam down to the surface of their ruined homeworld for a final doomed encounter that is sharply shot and edited. In the end, it doesn’t matter who was the dominant or subservient being: both fail to recognize their similarities and pay the ultimate price for their folly.

18. “This Side of Paradise”


“I have a responsibility to this ship, to that man on the bridge. I am what I am, Leila. If there are self-made purgatories, then we all have to live in them. Mine can be no worse than someone else’s.” – Spock

Was humanity meant to live an Edenic existence? “This Side of Paradise” explores that very question when the U.S.S. Enterprise investigates a colony destroyed by deadly ray beams on the planet Omicron Ceti III. Kirk, Spock, McCoy, Sulu (George Takei), and some redshirts beam down to the planet’s surface to discover that Elias Sandoval (Frank Overton) and his colonists are still very much alive and in perfect health, enjoying a pastoral existence off the grid. The colony’s botanist, Leila Kalomi (Jill Ireland), reveals harbored feelings for Spock after meeting him years ago, leading to her exposing him to the spores of a flowering plant that cause euphoria and loss of inhibition. The intoxicated Spock then confesses his love for Leila and agrees to live out an idyllic existence with her in the commune.

What follows is a drama of mutiny, temptation, and outright comedy. “I don’t know what I can offer against paradise,” Kirk frets as he struggles to maintain control over his pacified crew members who have been exposed to the contagion. Kirk’s goading of Spock into a physical confrontation makes for an entertaining sequence of both dialogue and action. But it’s the bittersweet ending of the episode which leaves a lasting impact. While Kirk wistfully reflects that humanity is not designed for paradise, Spock grapples with the realization that his time with Leila in the colony was the first time he truly experienced happiness. Here, writer D.C. Fontana takes us by surprise, allowing Kirk to take the intellectual lead and developing Spock’s half-human emotion, thus bringing well-roundedness to both characters’ stories.

17. “The Galileo Seven”


“It may be the last action you’ll ever take, Mister Spock, but it was all Human.” – Bones

“Totally illogical. There was no chance.” – Spock

“That’s exactly what I mean.” – Bones

In the first Star Trek episode to feature a shuttlecraft, Spock leads a scientific research team from the Enterprise aboard the Galileo on a harrowing mission that begins as an investigation of a mysterious quasar-like formation called the Murasaki phenomenon. Forced to make an emergency landing on Taurus II, a fog-shrouded planet in the middle of the quasar, Spock, and crew face off with a hostile tribe of Taureans, enormous ape-like creatures armed with devastating weapons. Although these violent creatures pose immediate threats to the crew, Spock goes up against his greatest enemy—his own logic—when faced with seemingly impossible decisions of command.

For the first time in the original series, Leonard Nimoy comes center stage and proves that Spock can effectively serve as the driving force of a Star Trek episode. All along the path of his mission, Spock’s logic is thwarted by random misfortune. “Strange,” he reflects. “Step by step, I’ve made the correct and logical decisions – and yet two men have died.” In the climactic moments of the crew’s desperate attempt to escape the planet, Spock makes an illogical gamble to save lives, which he promptly denies as irrational. “Mr. Spock, you’re a stubborn man,” Kirk quips during some delightful closing banter, which fantastically features that famous Leonard Nimoy eyebrow raise.