Star Trek is one of the most popular and longest-running franchises in all of TV history. The show has given us hundreds of great stories, and countless themes to dwell on. From Kirk to Picard to Sisko to Janeway and more, the captains of the various ships and their crews have imprinted themselves on our cultural consciousness.

It's one of those shows that's somehow accessible for any age group to plop down and watch, and yet almost never in its fifty years has it ever felt like it was aiming at the lowest common denominator. It's whip-smart sci-fi with a moral compass. When it's at its best, the show can be revelatory - providing seering insight into the human condition, pulling in viewers and having them put their personal beliefs and principles to the test. And even when it's not being so deep, it's still fantastic - making us laugh, cry, or jump out of our seats.

We wanted to put together a list of the show's high-water marks, the moments in its history when science and art and drama walked together in unison on the screen. So grab yourself a Romulan Big Gulp, sit back, relax, and enjoy Screen Rant's 20 Best Star Trek Episodes of All Time...

Warning: There may be SPOILERS for the Trek uninitiated

20. Take Me Out to the Holosuite (Deep Space Nine)

"Take Me Out to the Holosuite" does a wonderful job of exploring teamwork, and how the spirit of collaborating with others is so much more important than winning, or single-mindedly needing to always be the best. It’s a perfect example of what made Deep Space Nine such a great show, allowing characters to work together on another field of battle entirely – the baseball diamond.

A Vulcan ship arrives at Deep Space Nine, led by Captain Solok. Sisko remembers Solok from school, and the two have had a rivalry ever since. Solok, who is quite arrogant about his race’s physical superiority, challenges Sisko to a game of baseball in the holosuite. Baseball is Sisko’s most beloved game, so he takes the challenge very seriously, whipping his “team” into shape. He confides to Kasidy that Solok beat him in wrestling when they were younger, and so he couldn’t bear losing to him again. The game finally arrives, and the Vulcans decimate them, with a final score of ten to one. Sisko realizes that it doesn’t matter that much and that it was the journey with his team that mattered. This is an episode that shows a lot of humanity, and works well as a parable.

19. The City on the Edge of Forever (The Original Series)

While investigating space-time occurrences, the crew of the Enterprise is shaken up by one of the tremors. Dr. McCoy administers a relaxant shot to Sulu, but then accidentally injects himself when another tremor hits. McCoy hops into the transporter and beams down to the nearest planet. Kirk, Spock, and a skeleton crew go after him, and they find on the planet a hologram of “The Guardian of Forever,” who is, appropriately, the guardian of a time portal.

The Guardian allows Kirk and Spock to go through the portal and land at the same place and time as McCoy: 1930s New York City. The two look for McCoy but in the meantime take refuge in a hostel run by Edith Keeler (Joan Collins), who Kirk soon falls for. They find McCoy, but not before Spock learns that in this alternate past, Edith had spearheaded a pacifist movement which allowed the US to stay out of WWII and for Germany to create an atomic bomb. Spock stops Kirk from saving Edith’s life in a traffic accident, knowing that time must be restored for humanity’s sake.

The final episode of the show’s first season, "The City on the Edge of Forever" won the 1968 Hugo Award for Best Dramatic Presentation (the Hugos are kind of like the Emmys but for science-fiction).

18. Deja Q (The Next Generation)

A great episode about what it means to be human, Deja Q revolves around one character losing all superpowers and being forced to live as a mortal, if only temporarily.

The crew of the Enterprise arrive at a Federation planet, to check on a moon that is falling out of it orbit and could threaten life there. As they’re investigating, a naked Q (John de Lancie), an enemy, lands on their bridge. He tells them that he’s committed one too many crimes and has been kicked out of his sect, the Q Continuum, and has been stripped of all his powers. Data is placed in charge of watching him, and over the course of the episode we see how Q must adjust to being a vulnerable human. He enjoys food for the first time, gets attacked by Guinan, and then is later assailed by the Calamarain, who are seeking revenge for previous crimes.

Q escapes the Enterprise on a shuttle, and then has his powers restored. By the end of the episode he thanks Data for helping him cope with being human. It’s a funny, heartfelt, and action-packed good time.

17. Mirror, Mirror (The Original Series)

"Mirror, Mirror" works well on many levels, and it has great substance to go along with the action. Plus it’s pretty fun watching the actors pretend to be baddies.

An errant ion storm sends Kirk, Scotty, McCoy, and Uhura into a parallel universe. They land on the ISS Enterprise, a ship of the evil Terran Empire, which is the polar opposite of the United Federation. They come face-to-face with an evil Spock and Chekov, and learn that in this world, corporal punishment is commonplace among the ranks, and that the best way to get a promotion is to do away with one’s commanding officer.

Kirk surmises that it was an ion storm that got them there, and that their opposite selves must have been transported to their home universe. In the meantime, they have to fake being cruel war-mongers. But Spock notices their hesitancy towards all-out viciousness, and becomes suspicious. Kirk eventually shows Spock the error in his ways, and Spock helps the team escape home.

16. Measure of a Man (The Next Generation)

"Measure of a Man" is all about Data, and about what it means to really be human. While the Enterprise is docked for maintenance, a scientist working in the field of cybernetics, Commander Bruce Maddox, comes on-board and takes an interest in Data and how he works. Maddox requests that Data allow him to download the contents of his systems, so that he may better understand how Data’s creator, Dr. Soong, dealt with certain technical issues. The crew is weary of Maddox’s intentions though, and Data refuses, as he believes the scientist will disassemble him and use what’s garnered for nefarious purposes. Maddox goes to a Starfleet judge and asks his request be granted. Picard asks there be a formal trial first, which the judge grants, on the condition that Commander Riker acts as Data’s prosecutor in the case.

We get to see Riker versus Picard in the court room, debating what it really means to be human, to have a soul, and whether Data has those traits or not. We get plenty of wonderful lines here from both, as they try to woo the judge to their position. In the end, Picard wins the case. Riker feels guilt about having to argue against his friend, but is reassured by Data – yet another example of his humanity and a reminder that the right decision was made.

15. Space Seed (The Original Series)

Khaaaaan!!! Yes, this is the very first time we encounter the greatest Trek villain of them all, Khan Noonien Singh. The crew of the Enterprise comes upon a seemingly abandoned ship, the SS Botany Bay, and they board the vessel to investigate. Once inside, they see dozens of people in life-support capsules, all in hibernation. They discern who the leader is and bring him onto the Enterprise. The man awakes and is discovered to be Khan, the most dangerous surviving member of a race of superhumans who had run roughshod over Earth during the Eugenics Wars.

Khan uses his physical prowess, excessive confidence, and charm to take over the Enterprise. We see Captain Kirk for the first time being bested by an enemy, as he is tossed into a decompression chamber and used as a hostage against his own crew. But they rally and release their captain, who outwits Khan in a hand-to-hand battle. They cast out Khan into exile, believing it’s the last time they’ll see him.

Space Seed is great for a lot of reasons: We got to meet Khan for the first time, we saw how the tables could be so sharply turned on the Enterprise, and it didn't hurt that we got Star Trek II: The Wrath of Khan (1982) as a sequel.

14. All Good Things . . . (The Next Generation)

The series finale of The Next Generation, "All Good Things..." was a two-part episode that did a wonderful job buttoning up the show and leaving all of the characters on a high note. While investigating a possible anomaly near Romulan space, Captain Picard is shown going through temporal shifts, being transported twenty-five years into the future, and then back to the present, then six years into the past. To try to figure out the source of the anomaly and hopefully stop the shifts, he boards the ship of his ex-wife, Dr. Beverly Picard, in the future and asks her to help get him to the anomaly.

He finds that his nemesis Q has created the anomaly as a test for Picard to see if humans really can evolve. Using the shifting timeline to his advantage, Picard works with his past and future selves to destroy the anomaly through a coordinated attack. Afterwards, Q acknowledges that Picard passed the test, and the captain returns to the Enterprise for a poker game with his shipmates.

Television finales are often underwhelming, but this one-hundred-five-minute closer did a superb job of sewing it all up, even on such a long-running and illustrious series.

13. Trials & Tribble-ations (Deep Space Nine)

With Trek’s thirtieth-anniversary right around the corner, the show runners of Deep Space Nine wanted to do a special episode to pay homage to the original series. The idea was landed on to do a callback to "The Trouble With Tribbles" — which you might see further down this lis — and the team set to work using the cutting-edge effects to digitally insert characters into footage from the original episode. It went off without a hitch, garnering the best ratings of the season, getting three Emmy nods, and going down as another classic for the franchise.

Captain Sisko and his crew are carrying a Bajorian Orb and transporting a hitchhiker named Barry Waddle when they are sent back one-hundred years in the past. There, they find they are in the orbit of the USS Enterprise, and Sisko decides to board Kirk’s ship, albeit disguised in period uniforms. As the crew wanders the ship, they discover that Waddle was actually Arne Darvin, the conspirator from the original show who had poisoned the grain. Sisko discovers that Darvin has also planted a bomb on a tribble in an attempt to kill Kirk, and he has him apprehended.

"Trials & Tribble-ations" does a really good job paying tribute, and giving an old story its own twist with some subtance.

12. Count Down & Zero Hour - (Enterprise)

So, we’re cheating. "Count Down" and "Zero Hour" are actually two separate episodes, but together they play as one story, and represent the closing story arc of Enterprise’s third season.

One of the most action-packed episodes in Star Trek history, this one deals with a Xindi superweapon that must be disabled. The Xindi had come to revere The Guardians for lending their assistance to the race after a civil war had ravaged most of their resources. The superweapon they developed was going to be used to destroy Earth, as they had been forewarned that humans would seek to end their race in the future. One sect attempts to halt the mission though, as another is determined to forge on. Archer enlists the help of the Aquatics and others to help him stop the Xindi weapon, but The Guardians employ temporal shields around the weapon. Eventually, an Andorian vessel destroys the protector ship, which allows the team access to the weapon to destroy it.

This episode has pretty great special effects – so great it was awarded an Emmy Award for them. This is quite simply one of the best bits of Star Trek: Enterprise and has some amazing production value for a small screen series.

11. The Tholian Web (The Original Series)

"The Tholian Web" deals squarely with the idea of the ship losing its captain, and it illustrates Spock’s bravery and other strengths under duress. The Tholian web itself is an interesting technology, and would be revisited in later episodes.

The Enterprise is on a mission to track down another Federation ship, the Defiant, which had ceased all communication weeks prior. Their sensors alert them to fractures in the area. Kirk and a small team board the Defiant and find the whole crew dead. The Defiant is drifting towards a dimensional fracture, and Kirk orders his men out while he stays with the vessel. Spock tries to lock on to Kirk, but he disappears into the fracture along with the otherwise-empty ship.

A Tholian ship then comes along and demands that the Enterprise leave the territory. Spock requests a few hours for them to wait and see if their captain will reappear. The request is granted, but when the four hours are up, the ship attacks. Spock is able to offset the smaller ship's attacks, until a second Tholian cruiser shows up and the two ships begin creating a web around the Enterprise. If the web completes itself, then it would destroy the Enterprise. Spock commits to staying the course, as other members of the crew grieve for Kirk, who they believe is gone forever. But just as the Enterprise is about to be lost to the Tholian web or the fracture, Kirk is locked back on to and brought aboard. They are able to escape by shuttling through the fracture.

10. The Best of Both Worlds (The Next Generation)

One of the best-loved stories in The Next Generation, "The Best of Both Worlds" begins with the finale of season three, and finishes with the premiere episode for season four.

Receipt of a distress signal brings the Enterprise into range of a Federation outpost, which has been demolished by the time they arrive. Starfleet Amiral Hanson and Lt. Commander Shelby arrive on the Enterprise, and Hanson informs Picard that Riker has the opportunity to captain his own ship. The Starfleet crew’s suspicions that it was the Borgs who destroyed the outpost come to fruition when they’re encountered by a Borg ship, which attacks. The Enterprise escapes for a while, but is soon caught and boarded. Picard is captured by the Borg, and they leave in their vessel towards Earth. Riker takes command of Enterprise, and the crew tries to communicate with Picard, who has by now been assimilated by the Borg as one of their own, now calling himself “Locutus of Borg.” This is where the first part ends, and it makes for one of the best cliffhangers in TV history.

Kicking off the next season, using Picard’s knowledge of their plans, Locutus outsmarts the Enterprise at every turn. But Worf and Data sneak onboard the enemy vessel and save Picard. They use his Borg implant to influence the Borg systems, which destroys the ship.

9. Sarek (The Next Generation)

Ambassador Sarek of Vulcan, Spock’s father, arrives on board the Enterprise, as he is going to be facilitating a conference on relations between the Federation and Legarians. But as soon as he arrives, everyone on the ship starts acting out. Fights break out, people break down crying — something about the Vulcan’s arrival triggers peoples’ emotions.

Dr. Crusher and Counselor Troi determine that Sarek is suffering from Bendi Syndrome, which is a mood disorder that causes one to broadcast their emotions onto others. Picard confronts Sarek on this matter, who at first remains obstinate, but soon breaks down. He plans to call off the entire conference, but his wife Perrin recommends he mind-meld with someone else — temporarily transfer his emotional baggage — so he can attend the conference without any distractions. Picard volunteers to be his assistant with this. The conference goes off without a hitch for Sarek, although Picard finds himself cycling through a range of intense feelings. Afterwards, they mind-meld again and Picard relays to Perrin how much her husband cares about her.

"Sarek" is an excellent example of how Star Trek can deal with human emotions and nail it. For such a scientifically minded show, they writers and actors do a great job realistically confronting feelings. The moral of this episode is how we can all sometimes broadcast our feelings onto others, and how it’s in others that we can find some support.

8. Yesterday's Enterprise (The Next Generation)

One of the slickest storylines out there, "Yesterday’s Enterprise" focuses on time-travel, and the ethic of sacrificing oneself for the greater good. Picard and his crew come upon a rift in the space-time continuum, out which comes a damaged ship, the Enterprise-C. It seems that the ship has come from decades earlier. Just then, everything shifts radically - Picard’s ship transforms into a warship, and the space around them is filled with battle.

The crew doesn’t seem to notice, but Guinan intuits that something’s askew. She helps Picard to realize that they are in an alternate present, where the Federation is losing a tremendous war. Picard talks to the Enterprise-C’s captain, Rachel Garrett, about her team needing to traverse the rift again in order to set the future on a more peaceful course. At first she disagrees, and both parties take huge losses. But eventually she gets savvy to the fact that it is inevitable. Her team returns through the rift to an earlier time and a perilous yet heroic destiny.

This story feels more like a movie than most standalone episodes do. It has an epic story to tell, and does so beautifully.

7. Amok Time (The Original Series)

In "Amok Time," the story is about Spock and his relationship to his home planet of Vulcan. As the episode opens, Spock starts lashing out erratically, causing Kirk to send him to sick bay. Dr. McCoy checks out Spock and determines that he has a very high hormonal blood count, and is concerned that his Vulcan friend may die from the condition. Spock asks for a visit back to his home planet, and Starfleet rejects the request. He then breaks down and confides to Kirk that he is experiencing the dangerous effects of the "pon farr," a condition every Vulcan male goes through in which they must mate or die.

Kirk disobeys orders to help his friend, bringing them down to the Vulcan planet for the ceremony. Spock meets T’Ping, his arranged mate, but she has already found a mate in a male named Stonn. T’Ping requests Spock fight for her — not with Stonn, but with Kirk. Spock resents this decision, but the two fight anyways. Kirk begins to lose badly to Spock, and so McCoy swoops in to administer Kirk a shot, supposedly to help him acclimate to the atmosphere. In actuality, it’s a drug that simulates death, so Kirk and Spock can end the battle and return to the Enterprise unscathed. But before he leaves, Spock confronts T’Ping and Stonn, telling them that sometimes having someone or something “is not so pleasing a thing after all as wanting.”

6. Unification (The Next Generation)

An excellent two-part episode from the fifth season of The Next Generation, "Unification" brings with it a cameo by Leonard Nimoy as Spock, and it would go on to be one of the most popular episodes in franchise history.

Picard is notified by Starfleet Admiral Brackett that Ambassador Spock has gone missing, and there are fears that he may have defected to Romulus. Picard directs the Enterprise to the planet Vulcan, where he meets with Spock’s father, Sarek, to garner more information about his son’s whereabouts. Sarek provides the name of the Romulan politician Pardek. Picard heads to Romulus, where he and Data track down the senator, only to be ambushed and kidnapped by his bodyguards. In an underground bunker, they find Spock. This reveal of the legendary character completed the show’s first installment.

In part two, Spock explains to Picard that he has not gone off the reservation entirely — he is not defecting, but instead using unorthodox routes to try to establish diplomatic ties with the Romulans, with whom the Federation has long had rocky relations. Picard voices his concerns about the Romulans’ motivations, and Spock concurs, but like a true diplomat he does not stand down from trying to hash things out still.

"Unification" did a great job of bringing back a character from the original cast and not having it feel hackneyed. Nimoy is great, of course, and it’s a real treat to see Spock interacting with Picard.

5. The Visitor (Deep Space Nine)

"The Visitor" resides, along with "In the Pale Moonlight," as one of DS9's most popular episodes. Interestingly, both revolve around deeply personal missions, and each shines a light on the inner lives of Jake and his father Benjamin, respectively. Both deal with time travel and choice in one’s fate, and how principles as well as emotions get entwined in decision-making. "The Visitor" may be the most powerful allegory about loss and regret the show has ever seen, and it’ll shake up even the most hard-hearted.

Sisko takes Jake out on the USS Defiant to witness a rare wormhole inversion. Their warp drive is affected from getting too close to the wormhole, and the drive releases an overcharge that zaps Sisko from existence. Jake believes his father to be dead, and continues on with the mission. We see the years go on, as Jake continues with his life, and apparitions of his father appear to him, for fleeting moments. Jake goes on to become a great writer, but can never shake the loss of his father. By the end of the episode all is restored, and both father and son come away with greater appreciation for one another.

4. Year of Hell (Voyager)

However one feels about Star Trek: Voyager, you’d be hard-pressed to find somebody who doesn’t like "Year of Hell." This two-parter from season 4 is a bruiser: Captain Janeway and the crew of the Voyager enter into a Zahl-controlled territory. A small ship encounters them, self-identifies as part of the Krenim race, and orders them to turn around. Janeway ignores the seemingly innocuous threat, but then a massive ray transforms a bustling Zahl planet into wilderness, damages the Voyager, and increases the size of the Krenim ship.

The Krenim threaten the crew, explaining to them that they have a time-change weapon that they use to transform parts of the universe to meet their desires. The Voyager is able to escape capture, but it is badly damaged. Janeway orders the crew off to allied ships, and she steers the ship directly into the Krenim ship. This destroys the temporal weapon and resets the timeline.

This episode came out of nowhere for many Voyager viewers. It brought a storyline many didn’t expect from the season, and it shined with originality, excitement, and excellent special effects.

3. The Trouble with Tribbles (The Original Series)

The crew of the Enterprise is summoned via a distress signal to Deep Space Station K7, an outpost of Sherman’s Planet. Upon arrival they are greeted by Nilz Baris, a committee member on agriculture for the sector. He had sent the signal, not really out of distress, but rather so Starfleet would guard their stores of Quadrotriticale grain as it awaited transport. Kirk agrees and the crew takes their posts.

The Klingons show up, and tensions rise as they demand access to the station. Meanwhile, a trader named Cyrano Jones offers a tribble to Lt. Uhura. She accepts the adorable, fuzzy pet and brings it on board. Soon, the tribbles have multiplied exponentially, and they get into the ship’s systems as well as the precious cargo. But as overfed tribbles pile up dead, Dr. McCoy discovers someone has poisoned the grain. A Klingon is apprehended, but it is only a disguise of the culprit’s true identity: Baris's assistant, Arne Darvin.

"The Trouble With Tribbles" blends all the Trekian components we love, along with funniness of the crew’s reaction to the little tribbles. It remains one of the most beloved of all Trek tales, even receiving a few homages in the years since.

2. Inner Light (The Next Generation)

As the Enterprise exits the Parvenium System, it comes across a mysterious probe, which scans the ship and hits Captain Picard with an energy beam. He is rendered unconscious, and awakens on a strange planet called Kataan. On this planet he is not Picard, but Kamin, an ironworker. He is married to Eline and lives a quiet life in the town of Ressik.

Kamin discovers that his planet is stricken with drought, which will in time render the planet uninhabitable. The civilization doesn’t have the technology to escape the impending disaster. Years later, after his wife has passed on, Kamin sees a rocket get launched. It is the same probe from the outset.

Picard learns the probe was sent out to tell others about what happened to their race, just before he awakens back on the Enterprise. Though penned not by a Trek alum but rather a freelancer named Morgan Gendel, "Inner Light" is widely considered to be one of the strongest episodes of the entire franchise. It’s a trip into the life of another, with Hitchcockian melancholy.

1. In The Pale Moon Light (Star Trek: Deep Space Nine)

For the top pick in this list, we decided to go with something that is more of a deep cut: "In The Pale Moon Light," an episode from Deep Space Nine. In the episode, Captain Sisko is faced with real turmoil as he must betray his principles in order to try to save scores of innocent lives.

Sisko understands that the Dominion is waging a heavy toll on the Federation in battle, and that they will likely go after the neutral Romulans next. In order to get the Romulans’ attention on the matter without any evidence, he has a data log forged. In all, a criminal and ambassador lose their lives over his efforts, but millions are saved. We see Sisko pushed more to his moral limits here than any character has been before. This episode explodes the bittersweet complexity of compromise, and the duality of man. It’s sublime.

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What are your favorite Star Trek episodes of all time?