[[quoteright:287:[[Series/StarTrekVoyager http://static.tvtropes.org/pmwiki/pub/images/SulanDurstsFace_8843.jpg]]]]
[[caption-width-right:287:[[OrganTheft A face freshly pilfered off your shipmate]] is a [[http://memory-alpha.org/wiki/Vidiian Vidiian's]] idea of AFormYouAreComfortableWith.]]

->''"Space is disease and danger wrapped in darkness and silence."''
-->--'''Doctor Leonard "Bones" [=McCoy=]''', ''{{Film/Star Trek}}''

Generally speaking, where British kids had ''Series/DoctorWho'', American kids had ''Franchise/StarTrek''.

'''Note:''' please avoid [[Administrivia/ConversationInTheMainPage personal examples, anecdotes and natter]]. Feel free to tell us about how scary the Borg are, but we don't need to know how they made you hide under the bed.

Let's take it by series:
* NightmareFuel/StarTrekTheOriginalSeries
* NightmareFuel/StarTrekTheNextGeneration
* NightmareFuel/StarTrekDeepSpaceNine
* NightmareFuel/StarTrekVoyager
* NightmareFuel/StarTrekTheMotionPicture
* NightmareFuel/StarTrekIITheWrathOfKhan
* NightmareFuel/StarTrekIIITheSearchForSpock
* NightmareFuel/StarTrekFirstContact
* NightmareFuel/StarTrekIntoDarkness


* The Xindi [[BugWar Insectoids]] are enormous [[SerkisFolk computer-animated]] ants. Industrial Light and Magic gives us all the detail on them you'll ever want and then some.
* There was also the automated repair station that turned out to kidnap crew members and fake their deaths so it could [[PoweredByAForsakenChild use their brains in its computers.]] Archer blows it up in the end... but the final scene is it beginning to put itself back together.
* Worst of all, though, is the ''much'' more graphic portrayal of what happens to victims of ExplosiveInstrumentation. When the ship gets attacked, other Treks have the StarTrekShake and the occasional sooty HesDeadJim person. ''Enterprise'' has things like people on fire and screaming, or crewmen blown out into space when the hull is breached, twitching for a bit, and then stopping.
* Most of the episode "Strange New World" was creepy, but the worst was when they beamed up the crewman during a storm [[spoiler: and he materialized with sticks and debris embedded in his face and body.]]
* ''Singularity'' seems like a "Naked Time"-ish episode, where everyone is obsessed with tiny tasks and becomes extremely agitated. T'Pol is unaffected, so she goes to check if Doctor Phlox is also all right. He isn't. [[spoiler: He has become so obsessed with Mayweather's headache that he's going to vivisect his brain, seeming ''identical'' to the MirrorUniverse Phlox, and threatens to kill T'Pol for getting in the way of his experiments.]]
* In Doctor's Orders Phlox experiences hallucinations whilst he and T'Pol are the only member of the crew awake for a trip through radiation that is dangerous to humans. At the end, [[spoiler: it's revealed that Phlox was hallucinating T'Pol as well. She was really sleeping along with the rest of the crew.]]
* The above two examples, his decision to support genocide in "Dear Doctor" and his Mirror Universe counterpart being one of the ''least'' radically different in terms of personality, has lead more than one viewer [[AlternateCharacterInterpretation to suggest]] that Phlox is actually a [[MadScientist dangerous nut]], seconds away from [[JumpingOffTheSlipperySlope cracking]] and going on a killing spree!
* ''In a Mirror, Darkly'' takes the agony booth and shows what prolonged exposure can do to a person. Mirror Archer is apparently insane after ten hours in Phlox's invention; it's just that the culture's so toxic nobody can tell, and even if anyone can tell, they dare not say so aloud; [[spoiler:with Forrest dead, ''he's'' now captain]].
* "The Exile." Think serial-killer drama combined with "Beauty and the Beast." First, Tarquin tries to entice Hoshi with a form he thinks will be attractive to her... while whispering in her skull, making her hallucinate him on all the viewscreens in the lab, and generally causing her to think that she's losing her mind. (Again.) When he does make contact, he makes her stay in his house in exchange for his help and demonstrates that he's been rifling through her memories to the smallest detail--never once asking her permission to do this, even her more painful memories--and tries using them to convince her to stay. When that fails and she finds the graves of his previous "companions," he creates an illusion of Archer essentially ordering her to stay and then attacks ''Enterprise'' itself. She has to threaten to break his telepathy amplifier to make him let her go. FreudianExcuse or not, that is some major league creepiness.

[[folder:The Movies]]
* ''Film/StarTrekVTheFinalFrontier'': The [[JerkassGod jerkass]] EnergyBeing with near-divine powers that was thrown in as its BigBad. That nearly killed Kirk. Then we have its VillainousBreakdown...
* ''Film/StarTrekVITheUndiscoveredCountry'':
** After the Klingon moon explodes in a massive PlanarShockwave, the USS ''Excelsior'' is close enough to not only have to ride out the shockwave, but when they scan the moon, they learn that ''[[EarthShatteringKaboom most of it is now simply not there anymore]]''. They then receive one of the more disturbuing {{Distress Call}}s in the history of the franchise, a Klingon, surrounded by flames, screaming in panicked Klingon before the signal abruptly cuts off, followed by a Klingon officer tersely messaging them to tell them that there has been [[DeadlyEuphemism an accident]], and that Starfleet's assistance is ''not'' required.
** The attack on Gorkon's ship, from the Klingons' point of view. The ''Enterprise'', sent to escort them into Federation space for peace talks, unexpectedly opens fire on them, crippling them and knocking out the ArtificialGravity. Two [[FacelessMooks space-suited assassins]] beam aboard and begin [[ImplacableMan slowly and methodically]] marching through the ship, shooting helpless crewmembers as they float in freefall, unable to fight back or seek safety. Once they find their target, they shoot him in the heart, before calmly marching back the way they came and beaming back to their ship. Did we mention that, due to the lack of gravity, the Klingons' blood is left to ''float'' in blobs drifting through the air, trailing behind the wounded or dead crewmembers, in a rare exception to the BloodlessCarnage usually seen on ''Star Trek''?
** Also, the same attack, from the ''Enterprise'' crew's point of view. The ship they are escorting is being attacked, and by all indications, it was the ''Enterprise'' that did it, with the bridge crew and Mr. Scott urgently shouting at each other unable to agree on what their own conflicting comptuers are telling them, trying to figure out just ''what the hell is going on'' before the Klingon ship finally regains control and prepares to [[ThisMeansWar open fire on them in evident self defense.]]
*** When the Klingon battlecruiser recovers and comes nose-to-nose with the unshielded ''Enterprise'', the ship locks photon torpedos and prepares to fire. Kirk just stares, slack-jawed at the view screen for a full ten seconds. This is the first time in the history of Star Trek that we've seen Kirk [[OOCIsSeriousBusiness falter in the command chair]]. He doesn't order shields up, he doesn't order evasive maneuvers, and he doesn't charge weapons, or anything else we expect him to do. He just sits there, staring. . .and then he surrenders. It's terrifying.
**** What sells that part is the rest of his crew's reaction, ''especially'' Valeris', you know, an emotionless Vulcan.
---->Chekov: "Shields Captain?"
----> (beat)
---->Chekov: "Shields ''UP'', Captain?"
----> (beat) (Klingon Cruiser is now at point-blank range filling the viewscreen, torpedoes armed)
---->Valeris: (with barely contained terror) " '''''Captain! OUR SHIELDS!''''' "
** A bit of a fridge example: Since the 1960s, the phaser has represented a sort of holy grail in less-than-lethal weapon engineering; with their ability to subdue an individual ''or'' a crowd instantly with no noticeable lasting health effects. This film, however, makes a plot point of the fact that even phasers on stun are potentially deadly.
* ''Film/StarTrekInsurrection''. The flesh stretching process of the Son'a. Only somewhat Nightmare Fuel until head baddie Ru'afo [[spoiler:betrays Admiral Dougherty, killing him by subjecting him to a flesh stretching machine. Ow.]]
* ''Film/StarTrekGenerations''. When Data's newly-installed emotion chip overloads and he goes LaughingMad, it's ''creepy as hell.''
** Picard's family including Jean-Luc idolizing, CheerfulChild René--one of the very few children that Picard likes--[[spoiler: dying in a goddamned fire.]]
** After [[spoiler: Picard fails to stop Soran the first time and they're sucked into the Nexus]], it winds up destroying the planet they're on. And it just so happens to now include [[spoiler: everyone inside the crashed saucer section of the Enterprise. Which means every character we've come to know and love for the past seven years--- Riker, Data, Beverly, Troi, Worf--- ''they're [[KillEmAll all dead]]''. We even get to see some survivors crawling out of the ship's remains just as the planet explodes for good measure.]]
* ''[[Film/StarTrek Star Trek (2009)]]''. This movie is surprisingly tame compared to most Star Trek movies, but there are still a few moments:
** The indistinct voices heard inside the ''Narada'' at one point.
** The ''Narada'' is about twenty miles long, hideously overweaponed, and covered in blades and tentacles caused by uncontrollable Borg ''growths''. There is nothing Accidental about the ''Narada'''s NightmareFuel.
** Being beamed inside a cooling system.
** That EldritchAbomination monster on the ice planet.
** Then there's the early scene where [[ThrownOutTheAirlock a crewmember gets sucked out of a hull breach, their screaming silenced when they end up in the vacuum...]]
*** Flailing crewmembers being sucked into space seems to be the new continuity's equivalent of the [[ScreenShake Star Trek Shake]].
** Everything about the Battle of Vulcan: [[spoiler: several starships carrying ''graduating cadets'' obliterated and '''a whole planet with six billion Vulcans sucked into a black hole''' in less than an hour.]]
** When Spock is [[spoiler:choking Kirk to death for insulting his mother, there's a moment, just a moment, when there's a hint of a bloodlust smile on his face. It is ''creepy''.]]

[[folder:New Voyages]]
* "Blood and Fire" is about Regulan bloodworms. The ones the Klingons were joking about in "The Trouble with Tribbles". Regulan bloodworms are not funny. Or cute. Or harmless and useful, like the ones in ''Enterprise''. Point of fact, [[spoiler: they travel in gigantic swarms, and they eat people alive, and we get to see it.]]
** Even the Klingons are clearly terrified of them.