[[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 [[ConversationOnTheMainPage 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:
----

[[foldercontrol]]

[[folder:Original]]
* There's the classic "The Doomsday Machine", where a giant, bluish-green horn of plenty like machine is consuming everything in its path and the mighty USS Enterprise can't seem to stop it. Not to mention its massacre of the crew of another ship, identical to the Enterprise, whose captain the experience had driven completely mad.
** The machine is pretty much a preview of the Borg--unthinking, unfeeling, and feeding its insatiable hunger by devouring whole planets for unknown ends. Add to that that it is made of metal so dense that the entire Federation fleet could unload its entire arsenal on it and it wouldn't be phased, and is, by a wide margin, the most powerful weapon ever seen in the franchise (more-or-less on par with the [[Franchise/StarWars Death Star]]) and you have one pants-shittingly scary machine. And we never find out who built it, what they built if for, or if there are more of them out there somewhere[[hottip:*: Well, we do in the extended universe, but it is decidedly not canon]].
* "The Man Trap", with the shapeshifting alien that sucked the salt out of the victim's body.
* And the Horta: imagine a giant ''pizza'' out to kill you.
** At least the Horta turned out to be nice -- it turns out she was only [[MonsterIsAMommy defending her babies]]. The gigantic brain cells of "Operation: Annihilate!", on the other hand...
** They made Spock scream. '''Spock.''' Just trying to imagine the level of pain that would require is Nightmare Fuel all by itself.
*** Moreover, remember that Kirk's nephew, not a Vulcan, is facing potentially far worse pain, should he awaken from his coma -- and despite the joking around at the end, Kirk still has to tell the kid that his parents[[hottip:*:and perhaps his brothers too, though we never see them]] died in agony, along with a sizable amount of everyone he knew.
* In the episode "What Are Little Girls Made Of?" you have Ruk, played by Ted Cassidy (''Series/TheAddamsFamily'' Lurch). Imagine an extremely intimidating giant who is extremely strong and yet also moves with such deadly grace that he can grab you long before you can react.
** The nightmarish ending of the episode also counts: the Andrea-bot, wielding a laser pistol, utterly at odds with her programming - unsure of whether to love or to kill, embraces her creator, Dr. Korby[[spoiler:'s android double]] and Korby pulls the trigger, disintegrating them both. Kirk and Chapel look on in horror, as do we.
* "A Taste of Armageddon": The people just walk into the disintegration chambers, like they're off to work.
* The cloud creature in "Obsession". It's capable of space travel, phasers don't do squat against it, it can silently sneak up on its victims pretty much anywhere, and if it catches you it basically sucks out your ''blood'' without even leaving a mark.
** The return of the Cloud Monster of Death was the premise of a DC Star Trek Graphic Novel written, IIRC, by Chris Claremont.
* Korob and Sylvia in ''Catspaw'' relied on classic NightmareFuel.
** And the part where the RedShirt of the week beamed up to the ship, and then dropped dead? And then a scary voice came out of his ''dead'' mouth? Yeek.
* The Kelvans, who reduced a young yeoman to a polyehdral cube and then crushed her to dust! ("By Any Other Name")
* The Zetarians in "The Lights of Zetar". Non-corporeal energy beings who zoom around the galaxy so fast the ''Enterprise'' can't outrun them, searching for someone to possess so they can live out their lives. And if they can't possess you, they'll just kill you horrifically while trying. The woman who dies on the station spends several seconds with her face writhing uncontrollably and glowing several different colors, possibly in a very great deal of pain, before she dies. Even with the long-out-of-date and obvious special effects, the shot is still unnerving.
* Charlie X. He can age you, turn you into an iguana or leave your face quite blank, among other disturbing things. But that doesn't really do him justice. An EnfantTerrible RealityWarper StalkerWithACrush [[MindRape Mind Rapist]].
** The aliens who [[TouchedByVorlons gave him his powers]] and apparently raised him. They're apparently so creepy that Charlie ''himself'' is frightened of them. You know, the same reality warper who just spent the whole episode swaggering about invincibly, smugly confident in his own superiority, and now he's begging the same people he was just bullying not to let them take him away. Then the way his last plea of "I wanna stay" echoes when they teleport him off the ship...
* The episode 'The Trouble with Tribbles' is mostly a lighthearted comedy, but the scene at the end where dead tribbles fall on Kirk until he's standing nearly waist-deep in them is very... disturbing. It's the equivalent of opening the door to the attic and being bombarded with dead kittens.
** And the way that they just kept falling as Kirk was standing there, probably from being casually tossed aside by [[spoiler: Dax and Sisko]]. And it was played for comedy, ''twice''!
* Chekov under the effects of the HatePlague in "Day of the Dove." Seeing the goofy PluckyComicRelief character with a bad accent suddenly start attacking everyone and attempt to ''rape'' some poor lady while whispering creepy things to her was really... disturbing.
* Balok in "The Corbomite Maneuver". Both as young Creator/ClintHoward with that adult voice and the alien dummy he pretended to be were scary. The latter even more so because they put that image at the end of every closing credits: you had to see it if you watched every episode from the second season on!
* Khan Noonien Singh. Granted, he would get much worse in the second Star Trek film, but even in his introductory episode, "Space Seed", the man was frightening. During his attempt to take over the Enterprise, he makes it clear to Kirk that he isn't screwing around by locking Kirk, Spock, and Uhura in the bridge and shutting off Life Support there in order to get them and the crew to surrender. When ''that'' doesn't work, he forces them to watch each other die, one by one, via suffocation in Sick Bay's decompression chamber.
** Nobody deserves the hell that Khan and his followers were forced to endure between ''Space Seed'' and ''Wrath of Khan''. How many people were attacked by the Ceti Eel before they figured out what was happening?
* Almost everything about NOMAD from "The Changeling", from its genocidal mission to "sterilize imperfect beings" to sending Spock into a mind meld induced MadnessMantra to wiping Uhura's brain.
* The ''Constitution''-class ship is kind of bright and cheery with the red doors and uniforms and such, right? Well, when [[GhostShip everyone on it is dead or almost dead]], the emptiness is kind of creepy, creepy like an AbandonedHospital. Specifically, the ''Defiant'' from TOS: "The Tholian Web" and ENT: "In a Mirror, Darkly" and the ''Republic'' from StarTrek25thAnniversary were messed up real bad. It didn't help that Kirk and his landing party on either ship were stuck there without the ability to transport to the ''Enterprise'' -- that's right, no escape route despite being on ships falling apart at the seams. And in the former case, on a ship that is phasing in and out of reality as you know it.
** It was also a bit bad in "The Mark of Gideon" when Kirk is stuck on an eerily empty ''Enterprise''. Loneliness is a sort of hell, particularly for an extreme extrovert like Kirk. Oh, and ''hello'', right before the first ad break, a bunch of pallid faces fade onto the viewscreen without warning, just staring...
** And "The Tholian Web"; the idea of an entire crew gone stark raving mad to the point where they all killed each other.
* The agony booth from the episode that introduced the Mirror Universe, not to mention just imagining what life must be like on a day-to-day basis in the mirror universe...
** And the agonizers, the torture devices that crew members carry around on their own belts, forced to surrender them every time an officer is displeased with their performance.
* The Neural Neutralizer from "Dagger of the Mind". The device was originally intended to cure the mentally psychotic, but one scientist decided to make a few..."minor adjustments". Not only does it inflict as much pain as the agony booth, but the operator can make changes to a patient's personality and memories. In the off-chance someone taps into his or her true self, they are inflicted with intense pain, as shown by poor Dr. Van Gelder. Probably the worst part is when a person is in the chamber with the device at full blast and no operator present...
--->'''Kirk''': [[spoiler: Can you imagine a mind....''emptied'' by that thing?]]
* "The Alternative Factor," where the two Lazaruses are doomed to [[FateWorseThanDeath forever fight each other in between the two universes]].
* [=McCoy=]'s injuries during "The Empath". What's worse is that we don't see exactly ''what'' happened to him during that time.
* Gary Mitchell from "Where No Man Has Gone Before", especially the part where Kirk and Spock are monitoring him reading through the ship's library in minutes flat and he turns and stares at them with his creepy, silver eyes. Then there's his powers, being able to make an oasis in a barren wasteland, and wanting to use said powers [[AGodAmI to make himself a god]].
* A lot of people consider the scene in "Plato's Step-Children" to be [[CrowningMomentOfFunny hilarious, what with the Tweedle-Dee and Tweedle-Dum song, tap dancing, self-slapping, and Kirk giving a pony-ride to a very small man in a toga.]] While it's understandable to see it as funny on the surface, consider for a moment a race of people who can [[MindRape force you to do anything. Anything. On a whim. And not only that, but they can force you to feel anything, too -- they have Spock laughing and crying.]] Spock himself says it best: they could seriously injure or even ''kill'' you just because they wanted to or you made them angry. Without even breaking a sweat, with the power of their minds alone. And these people seem to have no moral compass. At all. Imagine the sheer horror of being forced to humiliate yourself and be caused pain just because someone else was selfish, bored, and ''could''.
** Not helped that those assholes (the psychics) more or less [[ForcedToWatch make Dr. [=McCoy=] watch the whole thing]] in an attempt to make him stay on the planet as their physician, not long after he saved their leader from dying.
* "Wolf In The Fold": The idea that a seemingly immortal being had been possessing and killing people for thousands of years just to feed on their fear.
* Evil!Kirk in "The Enemy Within", especially the scene where he tries to force himself on Yeoman Rand and stomps on a crewman for trying to stop him.
[[/folder]]

[[folder: The Next Generation]]
* Armus from the episode "Skin of Evil".
* The Doomsday Machine mentioned for ''The Original Series''? Another one shows up in the novel ''Vendetta''. It's bigger, it's faster, it's angry, it's ''haunted'' by {{yandere}} ghosts!
* Data's possession in ''Masks'' is pretty frightening. He asks Geordi what it feels like when someone is "losing his mind", then gives a perverse smile and adds, "Masaka is waking!"
* Nagilum. An immortal, nigh-omnipotent Elder Thing who, [[ForScience in the spirit of scientific inquiry]] and genuine curiosity, decides to study the phenomenon of death. In order to do so, it rips a great big hole in spacetime, traps the Enterprise therein, and makes with the empiricism. And it manifests as [[http://images.wikia.com/memoryalpha/en/images/1/1e/Nagilum.jpg a giant face floating in the void]].
** If that face in the void image wasn't creepy enough, keep in mind it's Nagilum's idea of AFormYouAreComfortableWith.
** Nagilum's creepiest line is worth mentioning:
---> "Is it also true that you have a limited existence?... you exist, then you cease to exist. You call it... death."
** ...Which immediately leads to a redshirt being killed by a forced heart attack.
*** No redshirt has ever died in quite the same way, either--going from calmly sitting at conn, to seizing with a terrified look on his face, and then falling pitifully to the deck in the fetal position, still looking terrified.
** And let us not forget Picard and Riker calmly and matter-of-factly deciding to self-destruct the ship with all hands aboard rather then have them be killed one by one by Nagilum. The conversation Picard and his Number 1 have over how long to set the count down to the ship's destruction is chilling. [[FromBadToWorse It gets worse]] when FridgeHorror sets in and we remember that besides the crew, the Enterprise is populated by a couple hundred civilians, many of them children. One can't fault Picard and Riker for wanting to spare their crew from the horrible screaming death we saw the red shirt subjected to, but the way they just give up without really exploring any other options is unnerving.
*** What options? They may as well have been trying to arm-wrestle Galactus. If they fought, they would have been destroyed. Threatening to deny their captor the chance to poke and prod them, and being fully prepared to follow through on that threat, was their only way of actually escaping. You'll note that they weren't killed in the end.
** They go to a ship that is the ''exact'' double of the ''Enterprise'', only there's nobody aboard at all, and there are strange inhuman screams echoing throughout the ship. Then Riker finds Worf, who is freaking out a little, and they ask each other if they were making the screams. They weren't. Then they find the bridge, and every door leads to one of the other doors on the bridge, so they're stuck and are visibly shaken when they return to Enterprise.
*** Worf pretty much lost his shit on the bridge of the doppelganger ship. "THERE IS ONE BRIDGE. ONE RIKER, ONE BRIDGE GRAAHHH."
* The episode "Phantasms", specifically the [[ImAHumanitarian cellular peptide cake]] (with mint frosting).
** Watching Data, aka the Nicest of Nice Guys, [[DissonantSerenity calmly]] ''stabbing Troi in the shoulder'' over... and over... and ''over...''
* The first revealing of [[LosingYourHead Data's head]], in a cavern in San Fransisco.
** Later on, time starts to go screwy and we get a glimpse of the energy-draining ghost things.
*** The Devidians, the race of aliens in question, were picked up for use in one of the "Weekly Episode" story arcs for ''VideoGame/StarTrekOnline'' recently, in the spirit of Halloween. The Devidians in the actual TV episode are nothing compared to the ones in game - they are in absolutely massive numbers, as opposed to the handful seen on TV, and their base of operations is the poorly-maintained innards of a space station that, until recently, was uninhabited since the days of ''The Original Series''. Worse still, from that point on, you'll occasionally see the lights flicker in the populated regions of the station, and a ghostly Devidian will run by, apparently unseen by everyone else but you...
* The [[TheVirus Borg]].
** The Borg Queen is introduced as a talking, disembodied head and shoulders being lowered down into the rest of her body (''shown being assembled'' in later appearances; apparently, her body's stored ''in pieces'' when not needed.) Part of the spine hangs from the head and wiggles around in the air until it's all put into place. The aroused look on her face in the moments after being put back together doesn't help.
** ''The Return'' managed to make the Borg even creepier than we saw in the movies. Vicious assimilated dogs, a giant construction/weapon drone (with a spiderlike "scuttler" that emerged from it), pumping organic parts inside the cube, and a multi-bodied engineered drone (only the first body has a head; when Spock asks what it does, he's told "It feeds the tubes."). If it were actually filmed....Yipes!
** You think the Borg are bad in their current form? [[http://ottens.co.uk/forgottentrek/creating-the-borg/ Here]] is some lovely concept art that shows what they were ''considering'' making the Borg look like, with such lovely little details as ''[[http://ottens.co.uk/forgottentrek/wp-content/uploads/2006/10/Borg-concept-art-by-Ricardo-Delgado.png visible intestines behind transparent plating,]] mobile, sea anemone-style hair made out of pipes, and'' '''[[http://ottens.co.uk/forgottentrek/wp-content/uploads/2006/10/Borg-concept-art-by-Ricardo-Delgado2.png razor-sharp sickles attached to the Borg Queen's frigging wrists.]]''' Creepy does not even ''begin'' to cover it.
** ''First Contact'' makes it a point to show how frighting Borg assimilation is starting with the ensign getting injected with nano-probes and having his skin turn gray and implants sprout from under his skin to the Borg montage where we see sickbay converted in to an assimilation chamber with the implants being installed.
** In their introductory episode, a drone beams into main engineering and scans the ship's computer. It takes two phaser blasts to kill it, but is immediately replaced by another drone, and when Worf fires again it's blocked by the Borg shields. The drone then starts seriously messing with the ''Enterprise'' systems while staring very creepily at Picard and crew.
** In Parallels you see a [[http://memory-alpha.org/wiki/File:Riker_gone_mad.jpg desperate and half-mad Riker]] begging for help from the alt-uni ''Enterprise''. In his universe, the entire Federation has been overrun by Borg, and he is the only man shown on the bridge. He is so desperate to prevent himself from returning to his own dimension that he tries to ''kill Worf and by doing so endanger all of the multiverses in the process''.
** Just one phrase can send shivers down anyone's spine: "''[[TheAssimilator I am Locutus of Borg]]. ResistanceIsFutile. [[OhCrap Your life as it has been is over. From this time forward, you will service us]].''"
* Q's behavior when the Borg where first introduced. At first he seemingly sent them into Borg space out of child-like spite. But to just coldly brush off the ''real deaths'' of eighteen innocent people as a ''bloody nose''.
--->"Oh, ''please.''"
** It's an unsettling reminder that Q, for all his puckish pranks and amusements, is genuinely a threat on his own, and he is so far above the Federation on the food chain that the lives of a handful of Starfleet officers mean absolutely nothing to him.
** Q in general could be seen as NightmareFuel. Though he does have humanity's best interest in mind, for the most part, he is still a [[JerkAssGod jerkish reality-warping alien]] who will gladly toy with you (mentally and physically) for his own amusement. Not only will he wipe out entire civilizations out of pure boredom, but he can also alter the laws of physics with little-to-no effort. And that's not even getting into how '''dangerous''' he can be when he's angry.
** In the best Q episodes, its impossible to know what his motives are, but every time he has been claimed to be operating as an agent of the Continuum he has been ruthless. Willing to execute Amanda Rogers--after possibly having already executed her parents--or imprison a fellow Q in a comet for [[AndIMustScream eternity]], were just...wow.
* ''The Next Generation'' also had an episode where a child's imaginary friend turned out to be an evil alien. So you have a cute little girl telling another cute little girl that if she won't play her way, she can just stay and die with all the others.
** Her [[CreepyChild creepy expression and line delivery]] all the way through the episode.
* Wesley Crusher may be a CreatorsPet, but the doctor's teenage son getting ''impaled'' and ''screaming'' isn't something you see every day.
* The first season was quite full of fuel. Watching [[spoiler:Dexter Remmick]]'s neck squirm and throb at the end of ''Conspiracy'' is still truly squick.
** After [[spoiler:they PHASER THE SKIN OFF HIS HEAD WHICH SUBSEQUENTLY EXPLODES.]] In one version of it, at least.
*** And then after that [[spoiler: his whole upper torso explodes and an alien parasite jumps out, so they blast that with their phasers, and then it explodes too.]]
*** The concept art [[http://memory-alpha.org/en/wiki/File:Conspiracy_(Andrew_Probert).jpg is quite terrifying.]]
* The time everyone on the ship but Data is slowly transformed into prehistoric animals.
* And the episode where the ship gets cleaned by an energy field slowly sweeping through it that will kill ''any living being it touches''. Of course, Picard and some thieves get caught on the ship when the field is activated. (One [[GoryDiscretionShot isn't seen dying]], but is certainly ''heard'' dying, screaming horribly.)
* One episode had a [[RedShirt Red (Gold) Shirt]] die by getting ''[[http://images.wikia.com/memoryalpha/en/images/b/b7/Vanmayterdeath.jpg phased halfway through the floor.]]''
* The episode where Dr. Crusher gets trapped on a deserted ''Enterprise'' in the collapsing universe may be far scarier than was intended. There's a particular kind of hopeless terror when the ''borders of reality itself are closing in on all sides''. A ''New Scientist'' article predicting that this might be what it would ''actually'' look like when the universe ends ''does not help''.
** People start vanishing and no one [[ThroughTheEyesOfMadness except Dr. Crusher]] believes they were ever there, not even the ship's computer. At least when the pocket universe started collapsing you knew what was going on.
** The collapsing universe part almost came as a relief. What would have been far worse was if Crusher had just been left there, completely alone on the Enterprise, with everyone she knew gone, no way of possibly running the ship by herself, and still having ''no idea what happened''.
** COMPUTER: "The universe is a spheroid region 705 meters in diameter." CREEPY.
* "The Next Phase", where Geordi and Ro, who were trapped in the alternate phase of reality, dealt with a guy by ''kicking him out into space through a solid wall''. They appeared at their own funeral as ghosts writhing in pain as the AppliedPhlebotinum of the episode revealed them to the rest of the crew.
** Applying FridgeLogic to this episode makes it even worse. It's established that the people who are out of phase aren't able to interact with matter. This means that the out of phase people don't need air, or else it would have been a very short episode. Given that they don't need air, we can surmise they probably aren't affected by changes in temperature or pressure. Now apply all this to the Romulan who got shoved through the hull of the ship, last seen drifting off into space unable to counter the momentum of the push that sent him through the hull. Instead of dying a relatively quick death from exposure to space, the poor bastard will instead drift through space until he finally dies of dehydration.
*** Apparently people out of phase are still affected by gravity and can feel pain. Add into this potential immortality and, well, he's going to have to drift by a sun or a star eventually...
* At one point in the episode "Night Terrors," Dr. Crusher hallucinates that an entire morgue full of sheet-covered bodies are ''sitting up on their slabs.'' It's unspeakably unsettling.
** That whole episode is made of nightmare fuel. Also noteworthy are Counselor Troi's psychedelic visions: ''Eyes in the dark''
** One of the more subtly creepy moments is when Picard is sitting in his office, and the door chime starts sounding... over and over and over... and you don't know or see what's causing it. Keep in mind, this is before you really start to realize what's going on in the episode, so the fact that ''no one'' is activating the door chime is [[NothingIsScarier freaky as hell.]]
* The entirety of the episode "Schisms," where the ''Enterprise'' crew are abducted and experimented on while they sleep by creatures from deep subspace. Particularly the scene where the abductees try to reconstruct their nightmares on the holodeck, ending with them standing around a creepy operating table in the dark with strange clicking and buzzing noises in the background. You can even see an abductee's hands climbing toward her face in horror as they get more and more accurate. Or perhaps the scene in sick bay where Riker learns that his arm has been severed and then reattached while he was asleep.
* That serious MindScrew in ''Frame of Mind''.
* The episode ''Identity Crisis'', wherein Geordi (along with a few others) contracts a parasite and is transformed into a bizarre alien creature. And that's how that species reproduces...
** The scene in the holodeck where Geordi is de-constructing the video footage shot on the original away mission, gradually removing all of the crew members that were present until there's one remaining shadow, and nothing causing it: the computer prediction of the shape that cast the shadow is a formless, faceless blob.
* The "psych test" Wesley undertakes as part of the Starfleet entrance exam. Everything about the test is terrifying, and it's also notably a rare season 1 instance where the CreatorsPet does not come out on top.
** And the fact that that was precisely the point of the test! Using your psychological profile to tailor-make the scenario that will be most difficult, and therefore most terrifying, for you. And they do this to every, single officer. Even Worf was still visibly shaken by his test, which presumably took place several years ago.
* "Sub Rosa" has Dr. Crusher seduced by an energy being who claims to be an 800-year old human ghost. It does this by absorbing into her, and she reacts with visible ecstasy. The being ends up taking over her mind and trapping her on his planet, all while claiming to love her and only wanting to make her happy.
** The moment where her grandmother's corpse ''sits up in its coffin'' during a lightning storm ''with demonic, glowing blue eyes.''
** Very fitting, as the script for that episode was based on a story written by AnnRice.
** The scene where the ghost first appears [[MirrorScare behind Beverly in her mirror]] could induce a heart-attack.
* In "The Child", Counselor Troi is forcibly impregnated in her sleep by a non-corporeal life form.
* Those... ''creatures''... from "Realm of Fear", those... worm-things, slowly coming into view in the middle of the transporter haze.
* "The Most Toys" features what's basically a phaser on steroids that boils its victims from the inside out, giving them a few seconds of unimaginable pain before they die. And we actually see a ''full body shot'' of someone being killed by it!
* ''[[EvilTwin Lore.]]'' When he first appears in "Datalore," he's vaguely creepy. Then you find out that he's a ruthless sociopath, and that's creepier. But it's during the scene when he kicks his deactivated brother in the head, twice, for no practical reason, that he becomes truly terrifying. He isn't merely pragmatically self-centered; he ENJOYS hurting people. And he's strong and fast enough to tear out your femur and stab you with it before you could scream.
---> '''Lore''': "Are you prepared for the kind of death you've earned, little man?"
* "Conundrum" presented the ''incredibly'' unsettling notion that the crew's mind could be wiped and the entire crew be turned against a technologically inferior civilization without even realizing it. Just the notion itself is ParanoiaFuel.
* The episode ''Violations'' is terrifying enough to watch as a child, but understanding the literal MindRape implications of the telepathic attacks pulls it squarely into AdultFear territory.
* "The Game", especially when Wesley goes to talk to Picard about starting an investigation. You see him putting something down as Wesley enters, and then after he leaves, Picard turns around and picks up a copy of the game without a word.
* ''Dark Page''. If you never thought ''Lwaxana Troi'' could be scary...
* TNG never got a MirrorUniverse episode, but the book ''Dark Mirror'' gives it a go, and it's ''nasty''. [[TheEmpath Troi]] as [[MindRape Mind Rapist]] and [[TheCaptain Picard]] as a murderous psychopath were bad enough, but then Good!Picard discovers that this universe perverted Creator/WilliamShakespeare into a twisted parody of the literature we know. He can't even bring himself to ''look'' at his antique copy of Literature/TheBible (presumably he wants to sleep sometime).
* What about the episode where the Enterprise gets stuck in a time loop and keeps repeating the same thing over and over again? Knowing what was going to happen - [[spoiler:that you're all going to keep doing this over and over again for the rest of eternity, and there's a good chance that whatever you're trying to prevent now, you probably did the same thing LAST TIME]] would be insanely creepy.
** Which is presumably exactly what the crew of the ''Boseman'' had been doing for 90 years, and would have been doing for the rest of time if not for Data.
* Moriarty's line about how he experienced "brief, terrifying moments of consciousness" while he was trapped in the computer memory banks.
** Moriarty's fate as noted in FridgeHorror, since we later discover without regular maintenance holograms can eventually suffer glitches that threaten to destabilise the entire program. In "Ship in a Bottle", Moriarty and his lady love are trapped in a portable holodeck and are able to have their HappilyEverAfter... until the program starts to degrade! And they have no way of signalling the crew for help when that happens! ''[[YouMonster You Bastards!]]''
* The Crystalline Entity. Yes, it may look like a giant space snowflake, but the thing is pretty damn terrifying when you think about it. You're living on a Federation colony, then one day this thing descends from the sky and begins consuming all life on the planet. It's practically impossible to evade, extremely durable, and there doesn't appear to be any way of tracking it or providing warning of its arrival. On the off chance you survive, the planet you're on will still have been left a barren wasteland. It can and will kill ANYTHING.

[[/folder]]

[[folder: Deep Space Nine]]
* The Death of MirrorUniverse Odo in "Crossover."
* Odo's physical decay in "The Die is Cast."
** Any time Odo is strung out and needs to turn back into his true form to rest, but he can't. The makeup effects are impressively {{Squick}}.
* In an episode in which someone is killing Kira's resistance cellmates, they send her messages saying "That's one", etc. as each person is killed, in a deeply creepy Saw-type distorted voice. Even creepier? [[spoiler:They use Kira's voice.]]
* In "Field of Fire", when the [[spoiler:insane Vulcan]] murderer is revealed, he says he committed his crimes [[spoiler:because it was ''logical'']].
** Another creepy moment happens [[spoiler:when Ezri and the villain, both using guns which can see through walls, '' find themselves aiming at each other, at the exact same time, from all the way across the freaking station]].''
* TheReveal that the [[ShapeShifter Changelings]] had infiltrated the Federation. "It's too late; [[WeAreEverywhere we're everywhere]]."
** While Sisko is dealing with dissension within Starfleet that's led to martial law, a Changeling (in the form of nice, fun O'Brien no less) stops by just to taunt him. "What if I told you that at this moment there are [[ParanoiaGambit only four Changelings on this planet?]] [[IShallTauntYou And look at the havoc we have wrought.]]"
*** And the reveal that the Founders weren't even directly responsible for the damage done in that episode.
* That lovely scene when the Bajoran woman ''hangs herself'' on the crowded Promenade.
* The Dominion has "Houdini" anti-personnel mines, which hide in [[SubspaceOrHyperspace subspace]] and make you "disappear" -- at a randomly chosen instance, not by predictable rules. So basically, if you have no way to detect them, nowhere is safe anywhere they've been laid, even places you've passed hundreds of times.
** There's FridgeHorror in this, too. Houdinis were poor anti-personell devices, and absurdly bad area-denial weapons; they exist ''only'' as weapons of terror--designed to torture the Starfleet personnel with constant stress and paranoia.
[[/folder]]

[[folder:Voyager]]
* ShowWithinAShow version: There's a sequence in a child's holodeck program in which a massive fire monster hops out of nowhere and burns the main character to [[NotQuiteDead what looks like death if the kid's not bright enough to figure out how to help him.]] Worse happens in some children's stories, but the Holodeck is '''virtual reality''' -- 3D, immersive, in your face, and by the 24th century, as realistic-looking as reality. The idea of any programmer making such entertainment for a child seriously stretches WillingSuspensionOfDisbelief.
** Unintentionally terrifying things in media made for children have been a staple [[TruthInTelevision since fiction began.]]
* What about the macroviruses? Giant germs that popped out of victims' necks, buzzed around like insects, and eventually grew from bug size to bird size to monstrous.
** Now imagine how much worse it must have been for Naomi Wildman. Bugs as big as her, and Mommy is sick.
* [[LotusEaterMachine Telepathic pitcher plant.]]
* And then there's Species 8472, for the BodyHorror they can inflict simply by ''touching'' you. They scare the Borg as much as Locutus and the Borg Queen scared some of us.
** It's not what they can do to you -- it's that ''they can defeat the Borg''. And not just defeat the Borg but do it ''[[CurbStompBattle easily]]''. To put this into perspective, whenever a Borg cube appears in Federation space there's usually a dozen or more ships mobilized to fight it and even then there's heavy casualties. At one point an 8472 ship was drifting, unharmed, among a bunch of Borg cubes, lazily taking pot shots at them and blowing each one away with one or two hits.
*** Just remember their introduction. Two Borg cubes float towards the camera and the 'We are the Borg...' speech is heard. BEFORE THEY FINISH, 8472 weapons fire and both cubes go BOOM without a chance to fire a single shot. It's that infamous speech trailing off as the cubes turn into nothing but debris that catapults it into High Octane.
** Species 8472 were introduced in an episode featuring a ''small mountain of mutilated Borg corpses''. '''Gah.'''
** And later on, they [[EarthShatteringKaboom blow up a Borg planet]]. If the [[StarWars Alderaan]] scene is scary, imagine this being done by a couple of Voyager-sized ships, with the beams first converging on a central one before hitting a planet - and instead of clear "Hit and Boom" one sees as the planet disintegrates piece by piece!
* The creatures the ''Equinox'' crew [[HumanResources harvested for their advanced warp drive]] were creepy, and they popped out of portals and as such could attack from ''anywhere'' without warning. Complete with [[ShakyPOVCam monster's-eye view]] of screaming crewmen as the creatures pounce on their faces. And what they do to you if they get you is at least as bad as Species 8472.
* It doesn't get worse than the Vidiians, though. Afflicted with a disease that wastes their bodies to the point where most of them make your average zombie look like a GQ model by comparison, they attack ships to harvest crews' organs. Instead of the usual [[EnergyWeapons ray guns]], their weapons ''teleport organs right out of victims' bodies.'' Skin is in demand as well, and many a {{Redshirt}} has been taken away only for a Vidiian to return still looking pretty rotted... except for the face, which now has human skin that doesn't fit very well. And ''only'' the face, not the rest of the head, furthering the glued-on-skin look.
** [[http://memory-alpha.org/en/wiki/Image:SulanDurstsFace.jpg A particular(ly gruesome) example.]]
*** It doesn't help that the Vidiian "phage" has been inspired by [[http://en.wikipedia.org/wiki/Necrotizing_fasciitis a real disease]], commonly known as [[ExactlyWhatItSaysOnTheTin flesh-eating disease]].
* "The Thaw" in which members of the crew are trapped in a dream-like computer program where they are held captive by, ridiculed and almost killed by, not a MonsterClown but a whole bloody [[CircusofFear ''monster circus'']]. The clown was the ringleader, played by Micheal [=McKean=] as a LargeHam. The part that I remember the most is when the whole circus sings out "A VI-RUS! A VI-RUS! HE THINKS WE ARE A VI-RUS!" in a chillingly demented way.
* "Scientific Method" in which the crew are being experimented upon by invisible (phased) aliens. When Seven of Nine alters her optical whatevers, we see the crew walking around with 'things' sticking out of them while being followed by alien scientists like labrats.
** And for extra pants-soiling fun, the scene where one of the aliens ''walks up to Seven and starts adjusting one of the unholy devices attached to her face.'' And we [[NothingIsScarier never get to see what it looks like]]. ''And'' Seven absolutely cannot react to whatever horrors she sees or else she would give the game away to the aliens and they would exterminate ''Voyager'''s crew as "failed test subjects".
* After enough "special moments" like this, the network all but started advertising it as a horror show. "Such-and-such happens on ''Series/TheSentinel'', and then ''Series/StarTrekVoyager'' unleashes another hour of terror." They're right!
* Kes screaming in "Persistence of Vision" and "Cold Fire." Major spoilers for the former - one of the best episodes ever - follow.
** ''Persistence of Vision'' gets special points for some of the hallucinations - the BodyHorror ones were awful, but perhaps even more so were the more LotusEaterMachine ones. Just think... a loved one appears to you and even knowing what's going on doesn't keep you safe - ''all you have to do is '''listen for about twenty seconds''''' and you wind up trapped, staring into space with God-only-knows what going on inside your head (the episode had some LessIsMore going; we don't know what happens to you when you succumb and become basically catatonic and that made it ''worse'' somehow.) And then the way it ended...
** ''Cold Fire'' also deserves a special mention for that nice scene in which Kes inadvertently [[causes Tuvok's blood to boil in a nice display of her ever-growing psychic powers.]]
* Those hallucinations and creepy whispers in "One", and the pure terror in Seven's voice when the Doctor goes permanently offline.
[[/folder]]

[[folder:Enterprise]]
* 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]].
[[/folder]]

[[folder:The Movies]]
[[index]]
* ''NightmareFuel/StarTrekTheMotionPicture'' The whole damn, [[LeaveTheCameraRunning interminable]] thing! THAT is terrifying!
** Actually, specific events in this movie are a great example. In this movie more than any other Trek production, every aspect of space travel in the 23rd Century IS TRYING TO KILL YOU! The transporter disintegrates the ship's science officer. Crewmembers make extensive use of space suits for EVA. Going to warp accidentally throws you inside an uncontrollable wormhole. And remember those 300-year old space probes? One of them is coming back, and it's dragging a giant machine thousands of miles long that is more than capable of rendering the planet Earth completely lifeless. What's more, it's been sent by a race of machines that don't even perceive carbon-based organisms as living beings. V'ger is looking for God, and if it doesn't find it, it will nuke your planet.
** Oh, dear god, that transporter room scene. When the crewmen start re-materializing there's an odd, electronic buzz that slowly resolves (almost before you realize what you're hearing) into the sound of the victims screaming in agony. While you're realizing what that sound is, you start to notice the the two humanoids forming on the pad don't look quite...[[BodyHorror humanoid]].
-->'''Starfleet Transporter Tech.''': ''Enterprise'', what we got back didn't live long...fortunately.
* ''NightmareFuel/StarTrekIITheWrathOfKhan'' gets away with a ''lot'' because the PG-13 rating didn't exist back then, so the movie went as far into PG as it could without getting an R rating:
** The thought that whatever happened on Ceti Alpha V since Kirk marooned the ''Botany Bay'' survivors there was sufficient enough to drive ''Khan'' of all people to the point of utter madness is pretty nightmare-inducing. In ''Space Seed'', Khan was himself a case of NightmareFuel; in the movie, he's gone completely psychotic.
** A {{Puppeteer Parasite}} is deposited into a helmet, which is then placed onto a restrained crewman's spacesuit. The crewman, and not any RedShirt, but ''Pavel Chekov'', is helpless to do anything but scream helplessly as the thing crawls into his ear.
** We see one of the scientists from Regula One get vaporized by a phaser. It's not ''quite'' an InstantDeathBullet, as we can hear the man's quickly fading scream of agony as he is vaporized.
** Some of the injuries suffered during the battles between ''Enterprise'' and ''Reliant''. Scotty's nephew, who we find horribly burned, and another crewman in the torpedo bay who gets engulfed in flames during the final fight.
* ''NightmareFuel/StarTrekIIITheSearchForSpock''
** The most graphic depiction of disruptor disintegration Franchise/StarTrek has ever shown. The victim grabs his head in agony as he falls back against his control console and is consumed by energy ''from the inside, out''.
[[/index]]
* ''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...
--->'''Energy Being''': '''''YOOOOOOOOOOOOOOOOOOOOOOOOOOOUUUUUUUUUHHHHHHHHHH!!!!!!'''''
* ''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-leathal 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/StarTrekFirstContact''. Dear god, ''First Contact.'' The Borg were bad enough in the TV series, but anytime they showed up in this one the movie actually turned from a sci-fi film into a damn horror flick. One of the scariest scenes is where a handful of crewmen flee inside a darkened room on the ship... and then ''several'' Borg lights [[OhCrap start flickering on within the room]]. It gets so bad that anytime we transition to Riker's party talking with Cochrane down on Earth it actually comes off as a welcome breather.
** The warp coolant that dissolves (and seems to vaporize) tissue on contact. It's inexplicably kept in gaseous form in an easily-breakable vessel in main engineering.
*** To be fair, it's easily-breakable by Data, who has been shown to have SuperStrength.
* ''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...]]
** 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''.]]

* ''[[Film/StarTrekIntoDarkness Star Trek Into Darkness]]'' has a few "fun" parts sure to keep you disturbed.
** [[spoiler:Khan crushing Admiral Marcus' head with his ''bare hands'']].
** It's bad enough being sucked out into space when the hull's breached: Now imagine the casualties of when [[spoiler: the ''Vengeance'' breaches the ''Enterprise'' hull '''while they're at warp''']].
** [[spoiler:Spock going berserk and almost beating Harrison to death]].
** Whoever does the sound of bones breaking does a ''really'' good job of making that cringe-inducing crunch.

[[/folder]]

[[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.
[[/folder]]


----