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What Are The Most Terrifying Aliens From The World Of Sci-Fi?

We've all got our favourite sci-fi aliens from ET who's just desperate to get home, to Tribbles the fury pests encountered by James T Kirk. But while some aliens are friendly and cute, others are the stuff of nightmares. Here is the list of the twenty most frightening extraterrestrials from the best science fiction television shows and movies.

20. Yautja - 'Predator'


The Yautja are a race of alien hunters who are intent on seeking out humans and other alien prey, collecting skulls as trophies of their kills. Predators are tough, backed by advanced technology and weaponry including a personal cloaking device and enhanced vision. They are fast in any terrain, whether on the ground or jumping from limb to limb in trees.

The Predator was first encounter by Dutch, played by Arnold Schwarzenegger in the 1987 movie, 'The Predator', since then there has been numerous sequels and spin-offs and a remake is due to be released in 2018.

19. Armus - 'Star Trek: The Next Generation'

Skin Of Evil - StarTrek TNG

Armus is pure evil, born as a by-product of a procedure in which an unknown aliens purged all evil and negative attributes from their race. The result was a black viscous liquid, which could take many forms, including that of a humanoid. He's sadistic and full of rage, having been abandoned on a barren planet. As part of his campaign of torment against the Enterprise crew who are trying to rescue the survivors of a shuttle crash on the planet, Armus kills Lieutenant Natasha Yar.

18. Sil - 'Species'

Sil - Species

What could be worse than an alien race that aggressively spreads across the universe by disguising itself as a hot woman in order to breed with population of a planet before annihilating them? In the movie 'Species', the alien Sil is played by Natasha Henstridge, a sexually aggressive alien of unknown species. It's capable of rapid growth and can bond its own DNA to that of other creatures through copulation, reproduction and other forms of genetic contact.

17. Heptapods - 'Arrivals'

Heptapods - Arrivals

The strongest kind of fear is fear of the unknown and that's what makes the alien race in the 2016 movie 'Arrivals' so scary. The seven-legged race are hidden within their smokey environment, the top of their bodies constantly out of view. Clearly they are a powerful and technologically advanced race but mankind's inability to communicate with this advanced species makes their unexplained presence on Earth even more terrifying.

16. Sandkings - 'The Outer Limits'

Sandkings - The Outer Limits

The Sandkings may look like harmless, small insects but these tiny beasts have come along way. They were hatched from alien eggs found in Martian soil samples and it turns out that insects from Mars are a lot smarter and more aggressive that those found on Earth.

They were given the name Sandkings by Dr. Simon Kress who discovered them in a 1995 episode of 'The Outer Limits,' but the aliens aren't content with staying in their sandpit for long. The creatures show team working skills, prove to be aggressive and deadly in large numbers. They eventually outsmart the researcher and break free.

15. Blue Demons - 'Galaxy Quest'

Blue Demons - Galaxy Quest

In the brilliant 1999 comedy-sci-fi movie, 'Galaxy Quest,' starring Tim Allen and Sigourney Weaver, we're introduced to a super-cute, baby-like race on an abandoned mining colony on Epsilon Gorniar II. However, things aren't what they and the crew of the NSEA Protector soon learn that looks can be deceiving as the blueish-aliens drop their innocent smiles and bear their razor sharp teeth.

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14. Unknown Race - 'Signs'


The 2002 M. Night Shyamalan movie, 'Signs' is another great example of fear in the unknown. We spend most of the movie waiting to get our first proper look at the alien invaders, although we do manage to see some fleeting glimpses of the unknown alien race, most memorably in a terrifying piece of amateur video shot at a children's birthday party.

13. The Silence - 'Doctor Who'

The Silence - 'Doctor Who'

The Silence are a religious order of alien beings which first appeared to the Matt Smith incarnation of Doctor Who. The show's executive producer Steven Moffat specifically created the Silence to be scarier than any other creature to appear in Doctor Who.

What makes this ugly alien race so terrifying is as soon as you look away from them, you forget you've ever seen them, your memory is wiped of the whole encounter. The coming of this race was teased throughout the 2019 series of Doctor Who using the "silence will fall."

12. Species 8472 - 'Star Trek: Voyager'

Species 8472 - 'Star Trek: Voyager'

Most aliens encountered in the Star Trek universe are humanoid and relatable but when Species 8472 appeared in the final episode of season three of Voyager, all that changed. The three-meter-tall, tripedal race is much more biologically and technologically advanced than any other species previously seen in the Star Trek universe, including the Borg who have been seem to flee from this race.

As they come from fluidic space, a totally different dimension, 8472 is physically very different to humans. Yhey lack obvious moths, nostrils and ears, and are incredibly strong, capable of dismember a human and ripping through spacecrafts bulkheads with ease.

11. Prawns - 'District 9'

Prawns - 'District 9'

In 'District 9' a species of humanoid aliens with dark thick shell-like skin, who are nicknamed "prawns" based on their physical appearance and behaviour, are a strong, intelligent race who are technologically advanced but arrive on Earth sick and malnourished in spacecraft in 1982. Their reason for coming to Earth is unknown, so they are confined to "District 9", a government camp that is located outside of Johannesburg. It's the Prawns strength which makes them truly terrifying, in one scene a Prawn is seen to rip a soldier's arm off by taking hold off it, placing his foot on his chest and kicking outward.

10. Clover - 'Cloverfield'


The terrifying monster, codenamed "Clover," which wreaks havoc on New York City in the 2008, J. J. Abrams movie 'Cloverfield' is probably not of extraterrestrial origin, but it is very alien to us. Although its origins aren't revealed in the movie, J. J. has since confirmed that "Clover" didn't come from outer space and is in fact a deep-sea creature with an unknown evolutionary history.

Wherever it came from, the towering monster is terrifying and unstoppable. It's around 300-feet high, with four legs and a huge finned tail. What's even scarier is that it's grey skin is home to thousands of dog-sized parasites creatures which are strong enough to take down a human.

9. Vidiians - 'Star Trek: Voyager'

Vidiians - 'Star Trek: Voyager'

It's the Vidiians desperation which has earned them a place on this list, they sick race was first encountered by the Voyager crew in the Delta Quadrant. Members of the race are disfigured due to devastating disease called the phage that eats away at their DNA and organs.

The only way the Vidiians have found to survive is to harvest organs for transplantation from living beings they encounter. Their advanced medical technology which allows them to instantly remove organs from their victims, combined with their grotesquely deformed faces makes them one of the scariest creatures Voyager encountered.

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8. Weeping Angels - 'Doctor Who'

Weeping Angels - 'Doctor Who'

"Don't blink. Blink and you're dead. They are fast. Faster than you can believe. Don't turn your back. Don't look away. And don't blink. Good Luck."
The Doctor
They're said to be almost as old at the universe itself and they look like regular stone statues, each of which is covering their eyes with their hands as if crying but don't turn your back on them, don't look away, don't even blink because the second you do they will come for you.

The Weeping Angels are so scary because you never see them move, literally in a blink of an eye they move across the room towards you. When they catch you they eradicate their victims by sending them into the past to live out their full lives, while the Angel lives off of the remaining time energy of the victim's life.

Weeping Angels are "quantum-locked" which means they don't exist while they're being observed, the moment they are seen by any other living creature they freeze into rock. In the sight of any other living thing they literally turn to stone, even when seen by each other, which is why they cover their faces to prevent trapping each other in petrified form for eternity.

7. Unknown Species - 'The Blob'

The Blob

First seen in the 1958 movie, 'The Blob' this alien is an amorphous, gelatinous creature of unknown origin that came to Earth inside meteorite. The blog can change its shape and size at will and consumes any living thing it can captures, digesting its prey chemically and growing more and more as it feeds.

The blogs unsettling appearance, the speed at which is eats its prey and its speed and strength are what makes this alien so terrifying, as well as the fact that it is impossible to kill, the only thing that seems to slow it down is freezing temperatures which cause the blob to solidify.

6. Martians - 'War Of The Worlds (1953)'

The  War of the World

'War Of The Worlds' is based on H. G. Wells' classic alien invasion novel. The movie follows the mysterious events in a small Californian town following the impact of a flaming meteor in near-by hills. As local scientists flock to the scene to investigate the burning impact site, it soon becomes clear that this is much more than a meteor and that they've unwittingly stumbled upon the start of an alien invasion by an unstoppable and advanced species from Mars.

The story is so scary that when Orson Welles produced a radio version of the novel in 1938, thousands of listeners were convinced it was real and fled into the streets of New York and New Jersey, many were treated in hospitals for shock, it's said some even suffered heart attacks.

5. The Borg - 'Star Trek'

Star Trek The Next Generation - Q Who

"They're carving us up like a roast."
Commander William Riker
The Borg are the ultimate villains, they're ruthless and intent of conquering the galaxy by assimilating every species they encounter. Acting as a collective consciousness, they can't be reasoned with, and they're quick to remind those who try that "resistance is futile."

The Borg are a terrifying race of biological humanoids with mechanical component grafted on to their bodies, including mechanical claw-like hands, enhanced eye pieces and personal shielding making them resistant to phaser fire.

They were first encountered by Capital Jean-Luc Picard and the crew of the Enterprise D in the second season of TNG in an episode called 'Q Who?' when the ship is transported to an unexplored region of the galaxy where they encounter one of the Borg's large cube-shaped spacecraft.

4. Daleks - 'Doctor Who'

Daleks - 'Doctor Who'

Daleks are the stuff of nightmares, since they appeared on screens in 1963 they've had children hiding behind the sofa and there's no stopping Doctor Who, there have been 12 incarnations of the quirk timelord meaning that every generation has been exposed to the terror of the Daleks.

Their blood curdling war cry "exterminate, exterminate" has been a staple part of the long-running sci-fi show for years and the Daleks never fail to display their lack of compassion for life as they indiscriminately irradiate any being they encounter, believing themselves to be the only life form worthy of inhabiting the universe.

Many people incorrectly believe that you can escape a Dalek by simply running up a flight of stairs, but Daleks don't have wheels, they glide along effortlessly on an anti-gravity plate, which of course means they can fly. We first saw a Dalek fly in the 1988 'Doctor Who' episode 'Remembrance Of The Daleks'.

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3. Greys - 'Fire In The Sky'

Fire In The Sky

Released in 1993, 'Fire In The Sky' is one of the most terrifying alien films ever made, the fact that the movie is based on alien abductee Travis Walton's real life encounter makes it all the more chilling.

The movie, set in Arizona in 1975 follows a small lumbering crew who encounter a saucer-shaped object hovering over the ground during their drive home from a day's work in the Sitgreaves National Forest near Snowflake. Curious to find out what this craft is, Travis climbs out of the truck and approaches it, resulting in him being struck by a beam of light from the craft.

Five days later Travis returns, alive but naked, dehydrated and traumatised. Following his return Travis experiences a series of flashback of his abduction by extraterrestrials. The flashback scenes aboard the craft show how the unknown aliens race which resemble the classic "grey" aliens treat Travis as nothing more than a subject for the cruel experimentation.

We learn very little about the sinister alien race in the movie or their purpose for abducting Travis and other humans from Earth. Clearly they are an advanced species and their advanced technology means they can pull someone up into their craft and there's no way of stopping them.

2. Harvesters - 'Independence Day'

Harvesters - 'Independence Day'

Known as "Harvesters," the mysterious, genocidal race in 'Independence Day' seems to exist for no other reason than to conquer planets and annihilating their inhabitants. They are ruthlessly aggressive and almost unstoppable with a fleet of spaceships, each of which is as big as a city.

The Harvesters which invaded Earth in 1996 wore armoured biological exoskeleton suits which enhance their physical strength and offer protection. They are slightly shorter and more slender than humans, and bluish-grey in colour.

This race of alien doesn't communicate audibly, instead they use a sophisticated form of telepathy, which they can also use to communicate their words with a non-telepathic species by possessing by attaching tentacles from their exo-suit to the victim's necks and using their vocal cords.

1. Xenomorph - 'Alien'

The Xenomorph - 'Alien'

Xenomorph first appeared in the 1979 Ridley Scott sci-fi/horror movie, 'Alien' which is still as scary today. The Xenomorph kills anything it encounters, it's one of the deadliest of all known alien species and its reproductive cycle is as terrifying as its shiny, black, vertebrate-like body and its toothed maw hiding a proboscis-like inner mouth.

The Xenomorph starts its life as an egg-like creature which releases and small arachnoid-like beast when it detects the presence of a potential host, such as a human.

This creature will then launch itself onto the host's face and impregnates it with an endoparasitoid larva, which later consumes the host from within and makes a bloody exit from the body through the chest.

Once it's left the body, the organism very quickly grow into an adult Xenomorph, with acidic blood, a protective exoskeleton, a long flexible tail, and an elongated domed head.
Face Hugger - 'Alien'

Since the 1979 original, the Xenomorph has appeared in several more Alien film, including 'Aliens,' 'Alien 3,' 'Alien: Resurrection' and the latest movie, 'Alien: Covenant' which was released in May 2017 and follows on from the 2012 movie 'Prometheus' which is set in the same universe.

The Xenomorph also features in the 'Alien Vs. Predator' series with The Predator, the very alien which started this list, bring us full circle.

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