Science fiction and horror have long gone hand-in-hand; it’s a classic combo with roots in time-honored literature, like Mary Shelley’s 1818 novel Frankenstein. Sci-fi horror really took off in the cinema in the 1950s, as the new technologies of the Atomic Age inspired paranoia the world over and began to be reflected in films like Godzilla and Invasion of the Body Snatchers. The hybrid genre continued to blossom in the decades that followed, giving movie fans innumerable favorites such as Alien and The Thing. Even popular slashers like Jason and Leprechaun have found themselves going to space.

Update October 11, 2023: This article has been updated with even more overlooked sci-fi horror films in honor of Halloween.

Sci-fi horror remains one of the most beloved of all film genres, with new and exciting entries into the genre released every year. In the margins between all the celebrated examples of the genre, however, are dozens of excellent films that, for whatever reason, didn’t have the lasting impact that others did on popular culture. In the list below, we’ve narrowed it down to 15 forgotten sci-fi horror flicks that deserve to be rediscovered.

Victor Frankenstein (2015)

A retelling of the classic Frankenstein story, Victor Frankenstein goes for a period-piece vibe with an emphasis on the relationship between the titular scientist (James McAvoy) and his assistant Igor (Daniel Radcliffe). Igor is not from the original novel, so the film acts as both a reimagining of the first half of Mary Shelly's novel while marrying it to the classic film adaptations of the popular story. Victor Frankenstein has an emphasis on being a period piece but also features plenty of horrific creations and shows the true monstrosity of the various creatures Victor Frankenstein could try and create.

The Quiet Earth (1985)

The Quiet Earth is a New Zealand production based on the novel of the same name written by Craig Harrison. While not a story filled with monsters, the film explores how humanity is its worst enemy. Zac Hobson is working on a secret project codenamed "Operation Flashlight" when one of his superiors activates the device, causing the sun to darken momentarily. Zac realizes that everyone on Earth has disappeared when he wakes up after the initial aftershock. Zac is nearly driven to madness until he finds two more survivors, but he soon realizes Earth is still condemned as the weapon is posed to trigger another flash that will erase the Earth altogether.

Metamorphosis: The Alien Factor (1990)

Metamorphosis: The Alien Factor, also known as The Deadly Spawn II (though bearing no narrative connection to The Deadly Spawn), is a low-budget horror film about a research facility that becomes besieged by an ever-mutating, bloodthirsty being from outer space. No, the storyline isn’t very original and the acting is admittedly quite bad, but neither of those factors is the main draw here anyway; Metamorphosis: The Alien Factor thrives in the special effects department. It is a practical effects lover’s dream, loaded down with fantastic rubber creatures, gloopy gore, and surprisingly convincing stop-motion effects.

The pacing is lightning fast, as the movie constantly throws new twists, turns, and monsters the audience’s way, meaning this little movie packs a punch way above what its meager budget should allow.

Creature (1985)

We’ll make no bones about it: cult auteur William Malone’s Creature is a blatant Alien rip-off. The thing is, it’s a very good one! It tells the story of two rival spaceship crews coming into contact with a dangerous alien monster on Saturn’s largest moon. What follows is a familiar story of creeping alien terror on a claustrophobic space vessel, albeit with some unique ideas thrown into the mix that make it stand apart from other Alien clones. One such idea is the ability of the titular creature to turn the crew members into drooling zombies that wreak havoc on the vessel, which results in a few ultra-creepy encounters.

Controversial German weirdo Klaus Kinski stars, and gives a typically atypical performance, which earns the movie a lot of lovable cult charm. Although the film is inescapably cheap, the sets look quite good, the creature is cool, and the atmosphere is thick with hopelessness and dread. If you love Alien and are looking for something similar to scratch the itch for more, look no further than Creature.

Forbidden World (1982)

Forbidden World, like the aforementioned Creature, is another lo-fi attempt at capitalizing on the success of Alien. What sets this one apart, however, is that it was produced by B-movie giant Roger Corman, who imbues the material with his distinctive brand of sleaze. Dripping with blood, guts, and slime, this vicious and surprisingly steamy sci-fi chiller sees a band of scientists becomes dinner for a ravenous monster while stranded on a remote planet.

The film features incredible practical effects, a truly creepy creature, and some sets designed by a very young James Cameron – one of the many careers that Corman would help to launch – and is well worth checking out.

Fiend without a Face (1958)

Fiend without a Face is a classic ‘50s drive-in movie that has unjustly slipped into relative obscurity in the decades since its release. It follows a string of mysterious disappearances caused by an invisible creature that lives on atomic energy. For most of the picture, the film is an intriguing, albeit a little slow-moving, sci-fi mystery.

What makes the film a should-be classic, however, is the final act in which the invisible entity begins stealing human brains and using them to attack the people that get in its way. An early and influential flick in the evolution of the “splatter” film, the bone-chilling latter part of Fiend without a Face boasts a great deal of impressive (and nasty) special effects work, especially considering the time that it was made in. The image of the crawling brain with a spinal column attached should be one of the most important in sci-fi horror history.

The Mad Doctor of Blood Island (1969)

The Mad Doctor of Blood Island is a Filipino horror film about an American pathologist landing on a remote island on which a mad scientist has unleashed an army of mutants created by splicing together human and plant DNA. It’s more than a little bit corny, but tons of fun and chock-full of exciting moments taken right out of pulpy adventure novels of the ‘40s and ‘50s.

From killer trees to green-hued plant-zombies, The Mad Doctor of Blood Island brings the sci-fi horror schlock in spades. Also worth checking out are the related Filipino horror films Terror Is a Man, Brides of Blood, and Beast of Blood.

Hardware (1990)

Cult filmmaker Richard Stanley’s debut, Hardware, is a hard-hitting post-apocalyptic horror jam that deserves way more recognition than it gets. It’s about a seemingly deactivated killer robot unexpectedly springing back to life and setting out on a killing spree amidst a war-torn America.

As Den of Geek describes it, “Its story, about a military robot putting itself back together and menacing a post-apocalyptic ghetto, is a familiar one, but Stanley gives it real verve – Hardware has a stylish, artistic edge that most low-budget genre films of the period sorely lacked.” Indeed, the action is beautifully rendered through Stanley’s expressionist compositions and colorful, Giallo-esque lighting choices.

The Fourth Kind (2009)

The Fourth Kind is an interesting film. Framed as a pseudodocumentary, the movie takes the form of dramatic reenactments of the events that happened in Nome, Alaska, when a psychologist under memories of alien abduction. Star Mila Jovovich even introduces herself in the movie, saying she will be playing the part of Abbey Tyler, the subject of the piece.

The Fourth Kind is an interesting examination of the alien encounter movie and marries the popular alien abduction story with the documentary/found footage genre that was starting to emerge at the time. The movie is largely forgotten as it opened shortly after Paranormal Activity and then was crowded out by big holiday movies like A Christmas Carol, 2012, and Twilight Saga: New Moon.

Xtro (1982)

One of the best alien abduction movies ever made, Xtro tells the story of a father who is abducted by aliens, experimented on, and sent back to Earth to care for his young son. Family drama and body horror ensue in this deranged movie, which is equal parts downbeat and gloriously graphic. The film conjures up a very particular atmosphere of dread, and excites with a number of creative and horrifying scenes, including one in which the young boy’s toys become sentient and terrorize his babysitter.

Lifeforce (1985)

Despite being one of Tobe Hooper’s best movies, Lifeforce has never quite gotten the recognition it deserves as one of the best sci-fi horror movies ever made. The film is about an evil and perpetually naked space vampire that roams around London, sucking the “life force” out of people and turning them into mindless zombies.

With show-stopping special effects, an epic scope that belies its budgetary restrictions, and great performances by Mathilda May, Steve Railsback, and Patrick Stewart, Lifeforce is an underrated gem. In the words of SYFY WIRE, “There's a distinct '80s B-movie feel to much of it, but Hooper's manic horror energy shines through, giving us some truly terrifying creature sequences along the way.”

Goke, Body Snatcher from Hell (1968)

Goke, Body Snatcher from Hell is a kaleidoscopic Japanese sci-fi horror movie about a group of plane crash survivors who encounter an alien being that possesses them, turning them into vampire-like creatures. Politically-charged and possessing an eerie, apocalyptic outlook, Goke is a tightly-paced and exhilarating creature feature that should satisfy fans of The Thing and Invasion of the Body Snatchers.

It’s bold, pessimistic, and full of raw emotion, and thus works as a fascinating example of horror reflecting the real-life horrors of the Vietnam War, as well as a prescient reminder of the fragility of humanism in contemporary society.

Prophecy (1979)

Prophecy is a little-known monster movie about mutated wildlife running amok on Native American lands in Maine. Like a wilderness-set re-imagining of Alien with an undercurrent of ecological subtext, Prophecy is a thrilling movie with a solid cast and impressive special effects.

Directed by the great John Frankenheimer, famed for his thrillers The Manchurian Candidate and Seconds, the film is stylishly made and highly effective at scaring. The main monster of the film is a giant mutant bear, which looks fantastic, and should be remembered as one of the most iconic movie monsters of all time.

Planet of the Vampires (1965)

Planet of the Vampires is a stylish sci-fi horror flick by Master of Italian Horror Mario Bava. It depicts the alien terror that befalls a group of astronauts after they land on an uncharted planet. Mixing sumptuous spacey visuals similar to those of the later Barbarella with his usual Gothic approach, Bava creates an extremely unique genre mash-up that packs a plethora of thrills and chills.

Surreal and striking, the movie is of particular interest to sci-fi fans today for its relation to Alien; Planet of the Vampires and Alien share many plot points and visuals, including that of a spaceship crew investigating a crashed alien vessel that was seemingly ravaged by another type of creature. Even without acknowledging its influence on Alien, however, the movie stands up well on its own. It’s a brightly-colored nightmare in outer space that should be more well-known than it is.

Phase IV (1974)

Phase IV is a hypnotic mind-melter about desert ants forming a collective intelligence and revolting against the people of an Arizona town. You’d be forgiven for thinking that premise sounds like ‘50s B-movie trash, but give it a chance; the movie is quite artistically done and given an emotional gravitas that makes it feel genuinely apocalyptic.

The only feature film ever directed by legendary graphic designer Saul Bass, the artist behind many of Alfred Hitchcock’s best films’ title sequences, the film is surreal, hallucinatory, and gorgeously composed. Its art-house stylings compliment its documentary-like approach brilliantly, and the whole thing straddles an interesting line between cerebral and deeply unsettling.