Science-fiction horror movies are the Reese's Peanut Butter Cup of film genres, blending two forms of entertainment into a bewitching mix that both fascinates and terrifies.

2017 is going to be a big year for sci-fi horror movies, with the première of Life on March 24, followed by Ridley Scott's highly anticipated Alien: Covenant on May 19 and the long-awaited adaptation of Stephen King's The Dark Tower on July 28.

Ranking this list was a pretty legitimate challenge, given the breadth of material such a genre combination allows for, and we've made the hard call that classic films like Aliens, Predator, They Live, and The Terminator, while occasionally described as horror, feel best classified as sci-fi action films, and therefore belong on another sort of list entirely. So with that criteria in mind, here's our list of the most terrifying, visually arresting, and thought-provoking sci-fi horror films of all time, from the golden age of Hollywood up to present day.

15. Event Horizon (1997)

Sam Neill as Dr. William Weir in his twisted state in Event Horizon

Event Horizon is one hot mess of a movie. Director Paul W.S. Anderson (Resident Evil) was the victim of studio meddling, resulting in a rushed production and drastic edits to his original work. Because of this, the film has a slapdash, frenzied, and disjointed sense of pacing. This didn't serve it well with critics or at the box-office, to say the least.

Event Horizon gained a second lease on life thanks to home video, however, with genre fans appreciating the film despite its flaws--noting the weird pacing has a hallucinatory charm, and that the basic storyline of a space crew investigating a space vessel imbued with an evil presence was engaging and unique for its time (and that it would go on to influence films like Sunshine and Pandorum).

The concept of a ship that doubled as a haunted house allowed for plenty of jump scares, and a prize turn from actor Sam Neill as deranged mad scientist Dr. William Weir makes this one all the more enjoyable. The scene of a smiling, bloodied and eyeless Weir is an indelible image of 90's horror.

14. Under The Skin (2013)

carlett Johansson Under The Skin

One of the most polarizing films of this century, Under The Skin certainly leaves an impression that fits its title. Scarlett Johansson stars as an alien disguised a human female with one simple, disquieting mission: lure men into having sex with her, then lead them into a pool of thick black liquid--and to their doom.

She is dispassionate in her pursuit, a clearly strange, biological need that keeps her alive. But her sexual predatory nature comes back to haunt her in the end.

Under The Skin was a box office dud upon its release in 2013, with an unusually slow pace and a mysterious open-to-interpretation plot that frustrated some genre fans wanting a more traditional alien invader narrative. But it's the film's uniqueness and departure from convention that makes it so haunting, intriguing, and unforgettable. It's that rare science fiction/horror movie that's also an art film, one full of gorgeous visuals, unsettling content, and a stirring, thoughtful performance from Johansson.

13. Invaders From Mars (1953)

Invaders From Mars

Imagine being a child, and realizing your parents have changed from being loving and supportive to cold, uncaring, and outright unrecognizable. That's the simple yet chilling premise of Invaders From Mars, where young David MacLean (Jimmy Hunt) witnesses a U.F.O. landing near his home. Soon, he discovers his parents are under mind control from Martian invaders, but when he tries to inform the local authorities, he realizes the aliens are taking over mankind on a grand scale. It's up to David and a pair of scientists to stop the evil extraterrestrials before Earth turns into a slave state.

Invaders From Mars' lurid visuals and eerie atmosphere have the quality of a nightmare (the screenplay was actually inspired by a bad dream) -- a unique mix of unnerving science fiction with the feel of a dark childhood campfire tale. It would prove deeply influential on a whole generation of filmmakers, including Steven Spielberg, John Carpenter, and Tobe Hooper (who would remake it in 1986).

12. Attack The Block (2011)

Attack the Block aliens

Every once in a while, a film comes along that's incredibly hard to define, simply because it's so fresh and inspired. Suffice to say, British sci-fi horror comedy Attack The Block had that effect on critics and audiences upon its release in 2011.

The film, which takes place in inner-city South London, follows a gang of trouble-making teenagers who encounter an alien invasion. The creatures are decidedly unfriendly, and they begin a killing spree across the urban landscape. It's up to the street-wise hooligans to embrace their inner-hero and defend their neighborhood from the evil extraterrestrials.

Attack The Block is an invigorating cinematic experience for a variety of reasons. The gang's London slang (which takes awhile to absorb; there's no shame in turning on the subtitles here, folks) is engaging, the visual appearance of the aliens (furry, eyeless beasts with glowing teeth) is striking, and it features a star-making turn from actor John Boyega, which would help him land a leading role as Finn in the new Star Wars film series.

11. Ex-Machina (2014)

Alicia Vikander in Ex Machina

The concept of artificial intelligence has fascinated and unnerved ever since it was first introduced into pop culture. The fact that it's now moving from science fiction to science fact makes it more pressing than ever before, and Alex Garland's Ex Machina explores many of the terrifying implications of a humanoid robot.

When programmer Caleb Smith (Domhnall Gleeson) wins a contest that grants him a weekend getaway with his company's reclusive CEO Nathan Bateman (Oscar Isaac), he's introduced to the lifelike robot Ava (Alicia Vikander). Bateman tasks Smith with testing Ava's capabilities and intelligence. At first fascinated by his project, Smith soon becomes concerned when Ava's responses lead him to believe she's being abused by her creator. His search for the truth has disturbing findings.

Ex Machina presents the true moral and societal dilemmas that confront scientists who explore A.I., as well as the threats and benefits it holds for humankind. It's a truly chilling examination of scientific theory; Turing tests don't get much more harrowing than this.

10. The Invisible Man (1933)

The Invisible Man Movie

This classic cinematic adaptation of H.G. Wells' novel stars Claude Rains as Dr. Jack Griffith, a scientist who creates a potion that can render him invisible. Thinking he's made the next great scientific discovery, his continued experimentation leads to an unfortunate side effect (insanity).

Soon, Griffith's depraved, violent nature makes him a menace to society, and he takes refuge in a small British village, where his deteriorating mental state and newfound powers make him a terrifying threat to the local denizens. The film then shifts into a chilling cat and mouse tale, with local authorities battling a threat that's literally out of sight, leading to an explosive finale.

The Invisible Man features some truly groundbreaking visual effects for its day, with wonderfully taut direction from sci-fi horror pioneer James Whale. Rains' unhinged, unnerving portrayal as the title character makes for one of the most memorable on-screen villains around, and the film still holds up handily today.

9. Scanners (1981)

Scanners 1981

Best known as "that movie with the exploding head," Scanners marks our first entry from beloved genre filmmaker David Cronenberg. He's one of the most notable auteurs in the realm of science fiction and horror, most specifically the sub-genre of "body horror," creating films with stories of bodily decay and physical mutation. It's a cinematic movement which he practically spearheaded singlehandedly.

Scanners tells the story of a group of humans known as "scanners" that are imbued with powers of telepathy and telekinesis. When a rogue group led by the villainous Darryl Revok (played by the always creepy Michael Ironside), it sets up a battle between good and evil scanners that features several spectacularly stomach-churning set-pieces.

In addition to the aforementioned exploding head, the image of a blank-eyed, gasping, vein-popping Ironside is one of the most disturbing and memorable movie images of the 1980s. Scanners remains one of the most shocking films from the Reagan-era.

8. Re-Animator (1985)

Re-Animator Poster Image

This loose adaptation of H.P. Lovecraft's 1922 novella Herbert West-Reanimator stars Jeffrey Combs as West, a disturbed medical student obsessed with trying to achieve immortality through medical science. Once he stumbles upon a reagent capable of resurrecting corpses, he's inspired to break new ground, despite the moral complications. But his attempt to reanimate the dead (with the assistance of his equally unhinged roommate Dan) comes with dire and unexpected consequences of the most disgusting variety.

Re-Animator is a horror cult classic for several reasons: it's splat-stick gory humor is inspired, providing unforgettably gag-inducing sequences. It hosts an array of terrific performances, and features top-notch direction by Stuart Gordon. All these elements have helped make an X-Rated horror film not just beloved by genre fans, but by critics as well.

It's Grand Guignol of the most inspired variety, providing new and novel twists on a cinematic formula that begin with 1931's Frankenstein (more on that in a bit).

7. Videodrome (1983)

An arm pointing a gun oozes out of a TV in Videodrome

Our second entry from David Cronenberg isn't just one of the most frightening sci-fi horror movies of all time, but also one of the strangest. Videodrome stars James Woods as Max Renn, the CEO of a UHF television channel that specializes in lowbrow programming to gain viewers.

Always on the search for the next big thing to boost ratings, he discovers and acquires a program called Videodrome, which features disturbing scenes of torture and murder. His delight at the show's success becomes muted, however, after his girlfriend (played by Blondie's Debbie Harry) auditions for the show and never returns. He begins to fear that the show he thought was fictional might be all too real.

Videodrome features some truly unnerving sequences which blur the line from erotic to revulsion (and one of the most memorable moments of body horror in cinema). It's also ahead of its time, predicting a world where reality television often humiliates contestants to the thrill and delight of audiences, while distracting viewers from the political actions affecting their lives to their detriment.

6. 28 Days Later (2002)

28 Days Later Franchise

Danny Boyle's harrowing horror film stars Cillian Murphy as Jim, a Londoner who wakes up from a coma only to find his hometown seemingly completely deserted. Soon, he learns that humankind has been savaged by a plague, the "rage virus," an affliction spread through blood and saliva that turns people into violent, mindless, murderous savages. Leaving with a group of survivors, they try to avoid infection and escape the city, looking for a sanctuary away from the madness.

Adapted from a screenplay by Ex-Machina director Alex Garland, 28 Days Later has been rightfully credited with reviving the zombie genre (The Walking Dead bears particularly striking similarities to the storyline), while giving it a twist: the "infected" move at lightning speed, making them a far cry from the slow, undead stragglers from Night of the Living Dead and its ilk.  This ratchets up the tension, making 28 Days Later one of the scariest post-apocalyptic horror films you'll ever see. It's sequel, 28 Weeks Later, is a surprisingly solid sci-fi fright flick in its own right.

5. The Fly (1986)

The Fly 1986 transformation

Our third and final entry from director David Cronenberg (we swear) is his repulsively effective remake of 1958 B-movie flick The Fly. And the Canadian auteur transforms that film's simple premise of an alien-human hybrid into one of the most disturbing body horror films ever.

Jeff Goldblum stars as scientist Jeff Brundle, who creates a device capable of transporting inanimate objects. Morbidly curious to see if it can do the same for organic matter, he fearlessly uses himself as a guinea pig, only to begin a revolting metamorphosis after a fly infuses with his body during the experiment. He soon becomes violent and deranged, acting in an animalistic, predatory fashion.

Unlike the original film, where the man-bug hybrid was an instantaneous result, Brundle's transformation is a slow and painful process, resulting in the loss of limbs and the eventual turn into a giant, mutated insect. The Fly features some gut-wrenching visual effects, but it's Goldblum's tortured, tragic portrayal of "Brundlefly" that makes the film so effective.

4. Frankenstein (1931)

Boris Karloff in Frankenstein

You can't make a list of science-fiction horror films and not include the one that started the genre. Director James Whale's gloriously ghoulish adaptation of Mary Shelley's 1818 novel of the same name is one of the most revered and influential films of the genre.

The story of Dr. Henry Frankenstein's (Colin Clive) mad scheme of reanimating an undead being composed from multiple corpses using arcane scientific methods (with the help of a lightning bolt) is a powerful narrative that still resonates nearly a century later. And Boris Karloff's iconic performance as the Frankenstein monster remains a revelation. His multi-layered portrayal, which is both terrifying, humorous, and at times deeply sympathetic, makes Frankenstein transcend its genre trappings, and attain a poetic beauty that few monster flicks possess.

Frankenstein is a true artistic triumph, and one of the best films to emerge from the Golden Age of Cinema. And despite the numerous Frankenstein sequels, remakes and reboots (the best being 1935's The Bride of Frankenstein), nothing will ever beat the original.

3. Invasion of the Body Snatchers (1978)

Leonard Nimoy Donald Sutherland Jeff Goldblum

Jack Finney's 1955 novel The Body Snatchers has been adapted to film multiple times (four in total), and while the most well-known is the original 1956 film Invasion of the Body Snatchers, Phillip Kaufman's 1978 remake is even more unnerving.

Whereas the original film plays as a metaphor on the Red Scare communist witchhunt of the 1950s, the sequel seizes on the rampant rate of divorce during the '70s, resulting from "me-generation" self-absorption that sent baby-boomers on a quest for self-help books and New Age remedies.

After extraterrestrial plant spores cause strange flowers to pop up in San Francisco, a group of friends (played by Donald Sutherland, Brooke Adams, Jeff Goldblum, Veronica Cartwright, and Leonard Nimoy) begin noticing that their lovers, co-workers, and neighbors seem like complete strangers, leading them to the terrifying discovery that aliens are taking over humankind. The idea that someone you know and love has changed their personality and ideals overnight is a terrifying concept, and Body Snatchers mines this paranoia to exquisite, unnerving effect.

2. The Thing (1982)

The Cast of John Carpenter's The Thing

A loose remake of the 1951 cult classic The Thing From Another World, director John Carpenter made a film that's both a profound study of paranoia, as well as a display of some of the most groundbreaking practical effects in cinema.

This tale of an all-male scientific research crew in the Antarctica sees them plagued by an alien species able to perfectly duplicate any living organism. One by one, the doomed crew are absorbed by the invisible enemy, making the survivors constantly question who among them has been infected. And it's up to the surly, gruff antihero helicopter pilot RJ MacReady (Kurt Russell) to determine who's who and stop the beast from destroying all of humanity.

Rob Bottin's effects work is as inventive as it is terrifying, and more often than not, it still looks better than any digital horror effects you'll see today. Unfortunately, these gruesomely effective visuals worked against it upon release, when critics claimed The Thing was style over substance, ending John Carpenter's relationship with large movie studios. Luckily, time has been on its side, and it's now recognized as one of the best horror movies with sci-fi trappings, as well as being the best remake of all time.

1. Alien (1979)

The Alien reaching for Dallas

Let's face it, when you think of sci-fi horror, Alien is the first thing that pops up in your head (or out of your chest). It's the perfect fusion of both genres--using our fear of bodily contagion as a catapult for one of the most insidiously unnerving stories in cinema.

Director Ridley Scott has basically said that he designed Alien to be a haunted house in space, and that's why it's so effective. Unlike Prometheus, which takes on more than it can thematically chew, Alien gives just enough info on the Xenomorph to freak out the audience and leave them watching on in horror as the Nostromo crew are picked off one by one after answering a distress call from a derelict vessel.

Thanks to H.R. Giger's groundbreaking design, the Xenomorph looks like no movie monster before or since, appearing both sexual and insect-like in nature (Giger would coin the term Biomechanical to describe his production design), launching a franchise in the process. As science-officer Android Ash notes when describing the beast:"I admire its purity." That choice quote also explains Alien's enduring appeal: pure, simple, unrelenting terror.

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Well that concludes our list of the best science fiction horror movies. What other terrifying movies from the genre would you add to the list? Tell us in the comments!

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