There's always been time travel in Star Trek; sometimes it's done well, sometimes less so. Occasionally it's been used in the movies too: Star Trek IV: The Voyage Home has Kirk and crew traveling back to get some whales, and the first two Trek reboots have regular visits from future Spock. But it's in the various series where they've used time travel not just to tell a fun story, but to reveal something about humanity, ask moral questions, and yes, give us a good time with some fun anachronisms and a change of wardrobe.
We've left out a few episodes that could be interpreted as time travel, when a character experienced another planet's history, like the brilliant "The Inner Light" from The Next Generation or "Memorial" from Voyager. These all take place in the same reality our characters live in. Some are more about personal stakes, and some affect the entire universe, which is probably why it always gives Janeway a headache; once you start bouncing around from one timeline to another, it can be hard to keep track of what's going on. So here, in all its glory and confusion, with examples from the original series (TOS), The Next Generation (TNG), Deep Space Nine (DS9), and Voyager (VOY), are the 18 Best Time Travel Episodes Of Star Trek.
18 "Tapestry" - TNG
Captain Picard is in cardiac arrest, Doctor Crusher frantically trying to save him, when he finds himself face-to-face with Q, who questions him about the artificial heart that's now jeopardizing his life. He tells Q that he made some foolish, regrettable choices in his past, so Q zaps him back to his days as a cadet, when he was, it turns out, a lot wilder than the Jean-Luc we know today. But when he chooses to avoid those mistakes this time, the impact on his life is that he's... boring. He's an assistant astrophysics officer, who begs Riker and Troi for a promotion and is told that he doesn't "take risks" or "stand out."
Q gives him a replay, and he once again gets into the bar fight that results in him being stabbed through the heart by a Nausicaan, thus restoring his life to the one he had. Crusher saves him. Afterwards, he confesses to Riker that by changing one thing, he unraveled the tapestry that was his life. A good bit of philosophy, that, and helpful to all of us who sometimes look back with too much regret.
17 "Shattered" - VOY
When you tally it all up, Voyager probably does more time traveling than any other ship in the fleet. This time, the ship gets fractured into different eras of its own history, so one minute Janeway hasn't met the Maquis, the next one Seska and the Kaizon have taken over, another one has the crew newly assembled after being trapped by the Caretaker. Only Chakotay, protected by a serum, is able to travel from one to the next. Wisely, he kidnaps Janeway and injects her with the same serum, because she's got a history of getting headaches from time travel and will want to put an end to it as soon as possible.
This one is extra fun for its look back at Voyager's history, showing us an angry B'Elanna, a vengeful Seska (who never disappoints), and a still Borgified Seven of Nine. It also disproves the recent theories going around that Voyager's characters didn't evolve over the course of the series; watching Chakotay try to convince the crew in each era that working together is their only solution shows us how far each character has come from that very first episode.
16 "All Our Yesterdays" - TOS
Kirk, Spock, and McCoy beam down to Sarpeidon to warn its people that their sun is going supernova. They meet librarian Mr. Atoz, who rushes them around insisting that they "choose" before it's too late. It turns out that the library provides gateways into different times and locations, and after hearing a shout, Kirk runs through one of them and Spock and McCoy follow. But they've gone to different places: Kirk's is full of terrified witch-burners, and Spock and McCoy are in an ice age. The people of Sarpeidon have been escaping the supernova into their own past.
The real story here is Spock's. He and McCoy meet the exiled and beautiful Zarabeth, and Spock falls in love with her. Challenged by McCoy, he realizes that he's reverting back to what ancient Vulcans were like: savage, emotional, even meat-eating. Since they haven't been "prepared" for their new timelines, they all must head back through the gateways. Spock doesn't want to go, but in order to save McCoy, he must. Once they're back, Spock is profoundly affected by the experience, and McCoy has gotten a rare glimpse into the battles Vulcans fight against their primitive, emotional natures every day.
15 "Children of Time" - DS9
The Defiant discovers an inhabited planet behind an energy barrier, and Dax insists on investigating. They push through the barrier, ship shaking all the way, and find the planet behind it inhabited by humans, Trills, and Klingons. They're told that when they try to get back through the barrier in two days, they'll fail, get thrown back 200 years in the past, and get stranded. The people on the planet now—all 3000 of them—are their descendants.
Kira, however, has no descendants; history reveals that she died from injuries sustained when they crossed the barrier. While one Odo remains aboard the Defiant, unable to keep his shape, the Odo from 200 years ago is still alive, and confesses his love to Kira.
The moral question: if they can find a way to break through the barrier successfully, they'll wipe out a 200 year-old civilization and 3000 people. If they don't, Kira will die and they'll never see their families again, giving them a time travel conundrum that makes the title of this episode particularly apt.
14 "Cause and Effect" - TNG
Jonathan Frakes directed this one, and it gave him a huge challenge: how do you shoot the same scene over and over again, with minuscule differences, and keep the audience interested, especially when it's all pretty mundane stuff up until the last minute? Of course, that last minute is a doozy, because that's when the Enterprise blows up, and the cycle begins again.
The Enterprise gets stuck in a time loop, and plays out its own destruction over and over again. The senior officers are playing poker. Then they're on the bridge. Then they encounter a phenomenon. Then they blow up. Around and around they go. So where's the time travel?
Well for one, they're reliving the same day over and over again. Eventually it starts to feel too familiar, and they get their first clue that something is happening on another level. When they finally figure it out, thanks to some clue-planting by Data, they break free, and meet Frasier. It's really Kelsey Grammer, Captain of the U.S.S. Bozeman, who's been trapped in that same loop for 80 years. "There's something we need to discuss," Picard tells him. Gently.
13 "Relativity" - VOY
Seven of Nine gets recruited by Braxton, Captain of a 29th-century ship, to save Voyager from a saboteur who uses a temporal disruptor to destroy the ship. As she bounces through time, appearing on Voyager when Janeway first takes command (long before Seven was freed from the Collective) as well as in the present, she slowly tracks down the device that's causing the temporal anomalies. But every time she travels through time and is retrieved, she becomes weaker; every trip damages her, and she won't be able to survive too many more.
It's a bit of a time travel detective story as she appears in timelines she shouldn't be in as well as the present, and then discovers that the saboteur is actually Braxton himself, who has a grudge against Janeway for something that comes up later on our list. Along the way, we get the fun of seeing Seven without her Borg implants, a ping pong game in which the ball freezes in mid air, and a quick throwaway mention of the Borg's attempts to prevent the Federation from existing in the movie Star Trek: First Contact.
12 "Blink of an Eye" - VOY
There's an original series episode, "Wink of an Eye," in which aliens who move at an accelerated pace take over the Enterprise. Because they move so quickly, the crew can't see them, and to them, the crew looks frozen in place because they're moving so slowly.
This concept moves from a wink to a blink on Voyager, where the ship gets stuck in orbit over a planet where a primitive, caveman-like society exists. While minutes pass on Voyager, years go by on the planet, which incorporates Voyager into its mythology as it is not only visible in the night sky, it's been causing earthquakes. The Doctor beams down to investigate, and in just a few minutes, he spends three years on the planet. He reports on how Voyager has affected everything there, from technology to philosophy and art, and that the tremors it creates are still a problem.
When the planet reaches the space age, they send an astronaut (Daniel Dae Kim) to Voyager. He heads home with Voyager's tech specs, and he returns, years later to him, with help; Voyager has inspired the technological advances that frees them, centuries after their arrival.
11 "Tomorrow is Yesterday" - TOS
This one plays the time travel story for laughs, mostly, and that's what makes it so fun. The ship gets trapped in the 1960s, is flagged as a UFO, and takes aboard American astronaut Captain John Christopher. As they try to determine the damage they may be causing to the past, they decide that since he's not really noted in the history books, it's safe to keep him on the ship, but further digging leads to the discovery that his unborn—in fact, not yet conceived—son is Colonel Shaun Geoffrey Christopher, who will head the first Earth-Saturn mission. Christopher must be returned.
Kirk and Sulu head down to earth to erase the evidence of the Enterprise, and Kirk gets caught, which gives us some fun scenes during his rather innocuous interrogation. In the meantime, another 1960s refugee accidentally ends up on the Enterprise, and his reaction when he runs into Spock makes us wish they had Worf on board as well.
It's a bit of a silly one, but their efforts to return inspire the "slingshot" effect that gets used again in "Assignment: Earth" and the movie Star Trek IV: The Voyage Home.
10 "Timeless" - VOY
An icy landscape. Two figures in climate suits. The shot widens, and we see that buried deep within the ice is the starship Voyager.
Harry Kim and Chakotay have located their ship, which crash-landed 15 years earlier, and they're determined to change history and save it. We switch back and forth between the two timelines, watching the crew make plans for their new quantum slipstream drive, and watching a much older, much more bitter Harry Kim as he tries to violate the temporal prime directive and save his ship from the mistake he made in his calculations that has haunted him for the last 15 years. He and Chakotay have stolen technology to do it, and are tracked down by Captain Geordi La Forge, who warns them that they are about to commit treason.
It's a high-action, emotionally intense episode, beautifully directed by LeVar Burton, and with but seconds to spare, (older) Harry realizes that the only way to save the ship is to sabotage the slipstream. His younger self is devastated by the failure, until Janeway shows him a message recorded by the older one, explaining what happened, and adding, "You owe me one."
9 "Little Green Men" - DS9
So many TV series have a Roswell episode; why shouldn't Deep Space Nine? A malfunction on their ship causes Quark, Rom and Nog to crash land in New Mexico in 1947, where they are held at a military base. The comedy gets started when the Ferengi's universal translators aren't working and they smack their heads, trying to fix them, so the army officers assume it's a greeting ritual and mimic them. This, plus the frequent use of tobacco--"If they'll buy poison, they'll buy anything!" --convinces Quark that he can make a fortune among these greedy, ignorant humans.
There are some great moments here, especially when they try to convince the army that they're part of an invasion force. "We've been studying you puny Earthlings for centuries and you're ripe for conquest," Nog tells them, hoping to generate some fear. But it's actually Quark with the agenda; he intends to use his knowledge of future technology to manipulate humanity, establish an economic empire, and get warp drive to the Ferengi homeworld long before humans, Klingons, or Vulcans get it. Fortunately Odo, who's sneaked along for the ride, has other plans, and eventually they find their way home.
8 "Endgame" - VOY
The series finale of Voyager sent the show out with a bang, and took us back and forth as Admiral Janeway, years after the ship's return home, travels through time to shave years off Voyager's journey and save the crew who didn't make it back. Like Harry Kim in "Timeless," she's got a bit of a guilt problem: Tuvok didn't make it back in time to cure the neurodegenerative disease that destroyed his mind, and Seven didn't make it back at all. She wants to shave over 20 years off of their journey, and recruits Tom and B'Elanna's daughter, the EMH and Captain Harry Kim to help.
This episode is rich with details. In the past, Chakotay and Seven have started dating, and B'Elanna and Tom are about to have a baby. In the future, Chakotay has died, and Naomi Wildman has a daughter, born on Voyager while it was still in the Delta Quadrant. We get to see Admiral Janeway arguing with Captain Janeway as they determine which course of action to take, and even the Borg Queen gets involved, and then defeated.
It's an intense, fast-moving finale, with a payoff worth waiting seven seasons for.
7 "Future's End" - VOY
Not only does this two-part Voyager episode boast guest stars Ed Begley Jr. and Sarah Silverman (in her first acting role), it also has a great story and a fun, Venice Beach setting. "We could have worn our Starfleet uniforms. I doubt if anyone would have noticed." Tuvok comments.
It all starts when a ship from the future tries to destroy Voyager for causing an explosion in the past. It's Captain Braxton from the 29th century, who fails in his mission and gets stranded on Earth in the 1990s. He becomes a homeless lunatic, and Henry Starling (Begley) steals his technology and builds an Apple-like empire. It's Starling, not Voyager, who will cause the universe to explode, and the crew tries to stop him with the help of a young astronomer, Rain Robinson (Silverman).
Like many of the examples here, it's a strong story with deep consequences and a series of fun-to-watch scenes along the way. Chakotay and B'Elanna get captured by redneck conspiracists, The Doctor gets a mobile emitter but experiences pain for the first time, and Tuvok and Paris ride around in a van and get take-out burritos.
6 "Past Tense" - DS9
Another beautiful two-parter, with a particularly magnificent performance from Avery Brooks. Sisko, Dax, and Bashir, through--what else?--a transporter accident get thrown back to San Francisco in 2024. They get separated; while Dax is found by a generous benefactor, Sisko and Bashir end up in a zone called the Sanctuary District, which is an overcrowded section of the city designated for unemployed and homeless people. Sisko remembers that a man called Gabriel Bell will sacrifice his life to change things.
There's a whole political story here, and they do end up disrupting the timeline. Of course this destroys the future they're from, stranding Kira and O'Brien in a Starfleet-free world. They're left alone to track down the others, which provides one of the few lighter moments, when they try a few different timelines before landing in the right one, especially when they run into some flower children in the 1960s.
But the heart of the story about social injustice, poverty, class, and rebellion, both in Bashir's horror that Earth could have treated its poor this way, and Sisko's determination to take the place of Gabriel Bell when he is killed before he can fulfill his destiny.
5 "Year of Hell" - VOY
There are a handful of stellar two-partners across the Trek franchise, and this one's in the top five. Guest star Kurtwood Smith plays Annorax, who flies around in a time ship changing history. His goals are both global and personal; he wants to restore his planet's role as a dominating force in the quadrant, and bring back his wife, who died in one of his temporal incursions. Voyager messes with his delicate calculations by popping up unpredictably, he takes revenge, and thus begins the year of hell.
We see Seven guiding a blind Tuvok and offering to help him shave, Janeway telling Chakotay to reprocess her birthday present for much-needed supplies as the ship endures one attack after another, and Janeway's moment of ultimate sacrifice, fired by a combination of determination and fury. Every time the time ship engages, as it wipes out civilizations, "restoring" the timeline, disrupting it, it builds up Annorax's obsession. "You can't imagine the burden of memory that I carry." he tells Chakotay. "Thousands of worlds, billions of lives, gone, brought back, gone again. I try to rationalise the loss. They're not really being destroyed, because they never existed. Sometimes I can almost convince myself."
4 4. "All Good Things ... " TNG
Another series finale, another tip-toe through the time tulips. A disoriented Picard interrupts a date between Troi and Worf to tell them he's been traveling back and forth through time.
Q has told Picard that he will cause the annihilation of humanity, and Picard bounces through three different timelines, desperately trying to figure out how he causes the destruction and what will fix it. Thanks to the time jumps, we learn that Troi and Worf had a relationship, Riker never forgave Worf, and Troi died with the two mens' differences unresolved. Picard retired to a vineyard, Data became a professor and owned a lot of cats, La Forge stopped needing his VISOR, Dr. Crusher married and divorced Picard and got her own ship, and the Klingons have taken over the Romulan Empire. We also get to see Tasha Yar again, in the past, and Miles O'Brien, who has long since left the Enterprise for Deep Space Nine. And yes, Picard saves humanity, as he always does, and always will.
There's a quiet, lovely moment at the end when Picard joins his senior officers at poker for the first time. "I should have done this a long time ago," he tells them, then ends the series' seven-year run with the words "Five card stud, nothing wild, and the sky's the limit."
3 "Yesterday's Enterprise" - TNG
This one's another fan favorite, because it brings back Tasha Yar and gives her a much more noble death ... for the moment. (There's more to her story, but we don't learn it here.)
The Enterprise goes through a temporal rift and everything changes. They're a ship in wartime, Starfleet is struggling, and Tasha Yar is still alive. They come face to face with a starship from the past, scarred from battle, and the two crews work together to repair it and send it back into its timeline to finish the fight. They know two things: one, it's a doomed mission, and two, it might save the Federation. The key to all this is Guinan, who convinces Picard that this timeline is all wrong and needs to be fixed. She keeps giving Tasha weird looks, which is how Tasha finally figures out that she's supposed to be dead, and asks for permission to fight with the older ship.
No need to spoil the rest, for the few who haven't seen it, but it's an action-packed episode full of emotional moments and gives much thought to the ebbs and flows of time and fate.
2 "City on the Edge of Forever" - TOS
Many fans consider this the best Star Trek episode of all time. Writer Harlan Ellison wrote the original story, which put a drug dealer aboard the Enterpise, but it was altered to make it more Trek-friendly, to his anger and dismay.
McCoy is accidentally injected with cordrazine, goes haywire, and beams down to a barren planet. They follow him and find the Guardian of Forever, a talking time portal. McCoy jumps in, and Earth's history is eradicated in an instant. Kirk and Spock follow, hoping to find him and restore all of their civilization.
What McCoy did was save the life of Edith Keeler, played to perfection by a young Joan Collins. She's a visionary, someone who, amidst the poverty and hopelessness of the Great Depression, shares Gene Roddenberry's optimistic view of the future. Kirk falls in love with her, but Spock's clever use of "stone knives and bearskins" reveals that she must die, because otherwise she'll change the world and America will never create the atom bomb.
There are some comedic moments in this one (not to mention that cringe-y "rice-picker" bit), but it's really about the Kirk/Edith love story, and the way one small thing--a traffic accident--can change the world, and break the heart of our Captain.
1 "Trials and Tribble-ations" - DS9
A surge of chroniton radiation takes Sisko, Dax, Bashir, O'Brien, Odo, and Worf back to the glory days of the U.S.S. Enterprise, when James T. Kirk sat in the command chair. They're orbiting Space Station K-7, which tells any self-respecting Star Trek fan that they've landed right in the middle of the classic episode "The Trouble with Tribbles." It turns out they're after the same villain too: Arne Darvin, a Klingon surgically altered to appear human, has traveled back in time to warn his younger self and get his revenge on Captain Kirk by killing him.
We get all the glories of "The Trouble with Tribbles," with all its due reverence. There's the bar fight, in which Odo, Worf, Bashir and O'Brien now participate, and Kirk's taking down of his men for causing it, with O'Brien and Bashir now part of the line-up. And now that we know Dax and Sisko were inside the tribble compartment, examining them for bombs and discarding them, we have our explanation for why they kept falling on Kirk so relentlessly. A centuries-old mystery solved! And p.s., Dax thinks Spock is hot.
The technical work on blending the new footage in with the old is flawless, making it the best time travel episode ever, and a perfect homage to the series that started it all.
Okay, we know we missed somebody's favorite: go to the comments section and tell us which ones.
The newest series, Star Trek: Discovery, premieres on CBS later this year.