Set Phasers to Fun!
The original Star Trek series only ran for three seasons, but its impact has lasted for decades. From philosophical quandaries to space-faring hijinks, TOS delivered some of the most iconic moments in sci-fi history.
We've boldly gone through every episode and selected the 20 absolute best. Whether you're a longtime Trekkie or a curious newcomer, these episodes showcase Star Trek at warp speed brilliance and remain beloved across generations of fans.
Starting with...
20: "The Enemy Within" (S1E5)
Captain Kirk splits into two versions of himself (one good, one evil). It's a wild, psychological ride that asks the question: what makes us whole? Shatner chews the scenery in the best way he knows how, and the concept still holds up decades later. It's classic sci-fi with a personal twist that shows Kirk's humanity and leadership at odds.
Star Trek: The Original Series S1E5: The Enemy Within Review, TrekLad
19: "The Naked Time" (S1E4)
A mysterious virus causes the Enterprise crew to lose all inhibitions.
Sulu brandishes a fencing foil, Spock cries, and chaos reigns. This one's a fun mess that dives into the characters' deepest emotions while maintaining a perfect comedic balance. It also sets up threads that resonate in later episodes.
Star Trek - A Pattern, Star Trek
18: "A Taste of Armageddon" (S1E23)
Two planets fight a war entirely through computers—and still send people to die. The premise is chillingly relevant, and Kirk's defiance of senseless tradition is peak Kirk. Smart, tense, and deeply philosophical, it's Star Trek delivering a cautionary tale with style and a punch.
"A Taste of Armageddon" | Treks for All Time, Completing The Shelf
17: "Mirror, Mirror" (S2E4)
Welcome to the Terran Empire! Evil Spock has a goatee. Kirk plays diplomat in a brutal parallel universe. It's wickedly fun and endlessly imitated, spawning an entire sub-genre of alternate reality storytelling within the franchise.
Kirk, McCoy, Scotty, and Uhura are in the Parallel Universe, April 5, 2063
16: "Balance of Terror" (S1E14)
Essentially a submarine thriller in space, this episode pits Kirk against a cunning Romulan commander. It introduced the Romulans and gave us tense, chess-like strategy. It’s suspenseful, elegant, and unforgettable—a cerebral episode that defines early Trek excellence.
Star Trek: The Original Series S1E14: Balance of Terror - Review, TrekLad
15: "The Menagerie, Part I & II" (S1E11 & S1E12)
A clever reworking of the unaired pilot, The Menagerie explores themes of disability, illusion, and freedom. Spock's loyalty to his former captain drives a gripping trial with some of the series’ most emotionally complex moments. It's a deeply moving meta masterstroke.
Star Trek TOS (Preview S1-E11) - The Menagerie (Part 1), RetroAlexander
14: "Journey to Babel" (S2E10)
We meet Spock's parents! Politics, espionage, and family drama collide aboard the Enterprise. Mark Lenard and Jane Wyatt shine as Sarek and Amanda, making this one of the richest character episodes in the series. Vulcan culture and diplomacy take center stage in this classic.
Star Trek - S2E10 - Journey to Babel - Intro, Get Your Nerd On
13: "The Devil in the Dark" (S1E25)
A monster killing miners turns out to be a misunderstood mother. This one’s a perfect blend of horror, heart, and forward-thinking empathy. Spock's mind-meld with the Horta is a highlight of the show, turning fear into compassion with one simple phrase: "Pain!"
Star Trek TOS: The Devil in the Dark, TrekChallenge
12: "Errand of Mercy" (S1E26)
Kirk and Spock try to defend a peaceful planet from the Klingons—only to learn the Organians are cosmic peacekeepers. It's a gut-punch of a twist and a smart commentary on Cold War tensions. This episode redefined what power means in the Star Trek universe.
Beginning Scene from the episode Errand of Mercy, April 5, 2063
11: "The Enterprise Incident" (S3E2)
A heist? Espionage? Vulcan mind games? Yes, please.
Kirk goes undercover, Spock seduces a Romulan commander (sort of), and the tension is chef’s kiss. One of the cleverest and coolest episodes that balances action, subterfuge, and interstellar flirtation.
Trek Challenge Review: Star Trek TOS
10: "Where No Man Has Gone Before" (S1E3)
The second pilot for the show was a bold tone-setter. When a crew member gains godlike powers, Kirk must make a harrowing decision. It's mythic, eerie, and sets the bar for what Trek could be. The moral weight lingers long after the final shot.
9: "The Corbomite Maneuver" (S1E10)
A deadly alien threat. A bluff involving fictional minerals. And a twist that turns menace into friendly misunderstanding. This episode defines the spirit of Star Trek more than most: brains over brawn, always. It also introduces young Clint Howard as the unforgettable Balok.
Star Trek: The Original Series S1E10: The Corbomite Maneuver - Review, TrekLad
8: "The Tholian Web" (S3E9)
Captain Kirk disappears into interdimensional space while the crew contends with reality-fracturing tension. The visuals are cool, the stakes are high, and Spock and McCoy’s growing respect shines through. It's a surreal, cerebral highlight of season three.
Star Trek -- Kirk Kisses Uhura by Frustrated Idealist
7: "All Our Yesterdays" (S3E23)
A time travel tale that traps Spock in an ancient ice age—and reveals a surprisingly emotional side of him. It's beautifully melancholy and quietly powerful, a hidden gem from the later seasons. A story of love, survival, and inner conflict.
Star Trek - S3E23 - All Our Yesterdays - Intro, Get Your Nerd On
6: "The Doomsday Machine" (S2E6)
A giant, planet-eating weapon threatens everything, and Commodore Decker spirals into a breakdown. High-stakes action meets emotional trauma in one of the most intense hours of Star Trek. The music, acting, and pacing are top-tier sci-fi suspense.
Matt Decker commands the Enterprise, Omega Trek
5: "Space Seed" (S1E22)
The introduction of Khan Noonien Singh, the genetically engineered tyrant. It’s pure charisma versus Starfleet protocol, and it set the stage for Star Trek II: The Wrath of Khan. An iconic villain origin story with lasting cultural impact.
Star Trek TOS (Preview S1-E22) - Space Seed, RetroAlexander
4: "Amok Time" (S2E1)
Spock in heat. A trip to Vulcan. That unforgettable fight music. Need we say more?
This episode blends Vulcan lore, emotional repression, and classic drama into one of the most quoted and beloved installments. Also: the duel between Spock and Kirk. Need we say more again?
Paramount, Star Trek (1966–1969)
3: "City on the Edge of Forever" (S1E28)
Time travel, doomed love, and moral heartbreak. Kirk must let the woman he loves die to preserve history. With a script co-written by Harlan Ellison, it’s a haunting masterpiece that transcends genre. Possibly the most tragic and human story in Trek.
Star Trek's "Let me help", spaceunix
2: "The Trouble with Tribbles" (S2E15)
Fuzzy chaos! This comedic gem introduces the most adorable menace in the galaxy. The writing is razor-sharp, the timing impeccable, and the episode stands as Star Trek’s most rewatchable delight. Klingons and grain disputes never felt so fun.
Star Trek: The Original Series - 1,771,561 Tribbles, IGN
1: "The Galileo Seven" (S1E16)
Spock leads a shuttle crew marooned on a hostile planet, forced to balance logic and leadership under pressure. It’s a Spock showcase, a survival story, and a defining character study. A pivotal look at Vulcan pragmatism tested by human crisis.
Star Trek: The Original Series S1E16: The Galileo Seven - Review, TrekLad
You Might Also Like:
The Best Sci-Fi And Fantasy Weapons
The Best Sci-Fi Movies On Netflix
