The 20 scariest aliens

While the Xenomorph might be the most famous extraterrestrials to appear in the Alien franchise, the Engineers are arguably even more terrifying. Partly, this stems from their sheer power since they played a key role in the creation of humanity itself, to say nothing of their very unsettling appearance, which manages to be both human and yet not. The fact that they also intend to destroy their offspring with a pathogen certainly earns them a place in the pantheon of the most frightening alien beings.

The Day the Earth Stood Still is a fascinating alien film since it distills so many of the fears and concerns of Cold War America. At the story's center is the being known as Klaatu, an emissary from an extraterrestrial race. Though human-like in appearance, there’s still something very menacing about him, particularly when he tells the gathered nations of the world that they could invite their destruction if they are not careful. The characters and the audience know that this is no idle threat, and the fact that he is so calm while delivering the threat makes him even more disturbing.

The Twilight Zone was known for its ability to tap into the pervasive anxieties of the postwar period, and who could ever forget the episode featuring the Kanamits? These aliens seem to have come to Earth to help humanity, but their seeming benevolence is but a mask for more sinister motivations: they plan to harvest and eat their new charges. This remains one of the most disturbing of all of the Twilight Zone episodes, as well as one of the most influential since it was even parodied in The Simpsons. 

American Horror Story: Death Valley might be one of the anthology drama’s weaker elements, but there’s no question that its alien invaders are still terrifying creatures. These beings impregnate humans in the hope of creating a race of alien/human hybrids that will slowly take over the Earth and displace humanity.  It’s precisely their ruthlessness that makes them so terrifying to watch, and as the series ends, it seems as if there is nothing to stand between them and a total genocide of the human race itself.

Village of the Damned takes a rather unique approach to the alien invasion story, positing that extraterrestrials manage to impregnate human women, who give birth to the blonde children of the aliens. The children are unsettlingly human in appearance, but they quickly show that they have powers that go far beyond anything that humans can command. They are frightening precisely because they are both human and not and, as such, represent the extent to which the human race so often contains within itself the roots of its own demise.

Pennywise might be most famous for its clown form (portrayed by Tim Curry and Bill Skarsgård in the film adaptations), but it’s important to remember that this horrible creature, with its penchant for devouring the children of Maine, is an alien in origin. Pennywise is frightening for children and adults because it manages to be both an alien and a murderous clown. This being is definitely one of the more unsettling and disturbing beings to have emerged from the fertile imagination of Stephen King.

The entity known simply (and accurately) as the Blob has made a number of appearances, including in the 1958 and 1988 films that bear its name. It’s one of those creatures that’s disturbing precisely because it has no real shape but is still ravenous. Anyone who has seen the ‘80s film, in particular, knows how ravenous it is and how it can and will devour anyone and anything that crosses its path. It’s the epitome of an amorphous entity that serves as the receptacle for so many of humanity’s deep-rooted fears about bodily autonomy (or the lack thereof).

Slither really leans into the grotesqueness of its horror, even as it leavens its approach with a healthy dash of humor. Its alien being, a parasite that manages to infect a man and become a tentacled being straight out of a nightmare. The film manages to strike just the right balance between creepy and funny, but there’s no question that the alien parasite is itself a creature designed to worm its way into the viewer’s mind, a reminder of how outer space remains a potent source of threat.

Apple TV has a well-deserved reputation for creating compelling sci-fi content, including the series Invasion, which chronicles the lives of various people across the globe as they contend with a hostile alien invasion. Though the creatures themselves only appear periodically, they are remarkably frightening. Their insect-like design makes them seem almost eerily familiar, even as their penchant for killing any humans that cross their path are lethal reminders that they are a threat to all human life on Earth. The fact that so much about them remains unknown makes them all that much more terrifying.

Though they are technically known as Krites, the term “Critters” has long been associated with the horrible little beasties that are associated with this franchise. They might look rather silly when it comes to their creature design, but this doesn’t take away from the fact that they are ruthless killers. If anything, the fact that they look borderline cute makes them even more terrifying, as it suggests that even seemingly innocuous creatures have the capacity to make themselves into voracious predators capable of devouring any human with which they come into contact.

Jordan Peele has repeatedly shown himself as one of today’s most visionary horror filmmakers. In Nope, he gives audiences an alien that is terrifying precisely because, at first, it seems to be a traditional flying saucer. In reality, however, it’s a relentless and very cunning predator that is capable of sweeping up an arena full of people and devouring them. The scene in which the camera focuses on several unfortunate people as they’re literally being digested by the creature — dubbed Jean Jacket — more than earns this creature its place in the pantheon of terrifying aliens.

Starship Troopers remains one of the most controversial and misinterpreted sci-fi films that emerged in the 1990s. It’s a fascinating look at the way that militaristic fascism takes root, and, as a bonus, it also includes an alien enemy — known as bugs, though they are more officially called Arachnids — that are as unsettling as they are compelling. The fact that the creatures are sentient and possess extraordinary intelligence makes them even more unsettling, both for the characters who encounter them and for the viewers who see them on the screen.

While Pitch Black  might not have reinvented the wheel when it came to alien movies, it was nevertheless a compelling piece of filmmaking, largely thanks to Vin Diesel’s performance and the design of the alien creatures, often known as bioraptors. With a design that is evocative of both pterodactyls and the xenomorph from Alien, these creatures are ruthless and efficient killing machines. The fact that they can only hunt in darkness grants them an even more ominous aspect, and they are truly like something conjured out of humanity’s worst nightmares.

The novel The Body Snatchers has been adapted several times for the big screen, but one thing remains the same in each iteration: A group of aliens essentially replace humans with replicas that lack emotion (or, arguably, a soul). Part of what makes these aliens particularly scary is the extent to which the central conceit has proven so flexible when it comes to expressing American society’s anxieties and concerns, whether it be of Communist infiltration in the 1950s or the collapse of societal norms in the 1970s. 

Ever since the Predator first appeared in the movie that bears its name, it has exerted a powerful hold on the cinematic imagination. Though not as viscerally terrifying as the xenomorph — with which it has often done battle — the Predator (also known as the Yautja) is still unsettling, both because of its design and because of its behavior. Who, for example, could ever forget those moments when a Predator turns a human being into nothing more than another of its trophies? The Predator is a reminder that human beings are far from the only killers to be found in the universe. 

When it comes to terrifying extraterrestrials, they don’t come much more unsettling than the xenomorph, the title creature of the Alien franchise. Any time this fearsome creature enters the stage, the viewer knows that things are going to get very ugly and very brutal. Whether in the form of a facehugger or a chestburster or its final, adult form, this being is indeed the perfect predator, and both its design and its behavior allow it to burrow into the human mind, preying on the deepest fears people have about just how penetrable their body is and how they might not be on the top of the food chain after all.

John Carpenter’s The Thing might not have been an enormous success when it first hit theaters in the 1980s, but it has become a true horror classic. At the center of the story is the creature of the Title, which has the ability to take the form of other organisms. The film definitely leans into body horror, which is precisely what makes this particular alien so terrifying. It forces the characters and viewers to wonder just how much any person is really their own self and, just as unsettling, whether anyone else is, either.

M. Night Shyamalan’s Signs may not be the director’s best work, but there’s no question that the aliens that are the primary antagonists are still quite frightening. No one who has seen the movie can forget the moment in which the alien walks across the alley, and it is arguably the scariest and most disturbing moment in the entire movie. Moreover, the fact that the aliens remain largely off-screen for so much of the film allows them to take on an ever more unsettling presence in the viewer’s mind, making their appearances even more unsettling.

Steven Spielberg offered his take on the classic H.G. Wells’ novel War of the Worlds. These aliens are utterly ruthless in their quest to conquer Earth and turn all human beings into nothing more than fertilizer. The scene in which the aliens are shown spraying human blood and tissue over the red vegetation they’ve introduced sears itself into the brain. Though they are ultimately defeated by the microbes to which they have no immunity, they are nevertheless a very real and potent threat to humanity’s existence right up to their demise.

A Quiet Place is an extraordinary series for many reasons, but the franchise’s aliens deserve special mention. Not only are they terrifying to behold, but their ability to hunt exclusively by sound makes them a particularly potent threat to humans, who really, really enjoy being loud. They are made even more unsettling by the fact that they are almost indestructible, and even though there are signs that they might yet be defeated, the various movies make it clear that this is going to be a Herculean undertaking for the entirety of humanity.