11 Most Terrifying Sci-Fi Movie Monsters

Cinema's most frightening out-of-this-world creatures...

Dune Sandworm
Herbert Properties LLC

Fear is often based on the unknown and what's more unknown than the vast reaches of outer space?

Science fiction has always been as much about scaring audiences with visions of unearthly terrors come to wreak havoc on unknowing people as it is about exploration and aspirations towards a better future. Monsters have been a part of the genre since its inception, arguably the very first science-fiction novel Frankenstein was all about a creature wreaking havoc on the life of our protagonist and driving him to mania.

Whether it's alien lifeforms with life-cycles that involve very human body horror, a hitherto-unknown creature that can kill you in seconds just from mere act of walking, or the incorporeal forces of Hell itself, sci-fi gives creators the opportunity to dredge up the already unsettling parts of the normal human experience and amplify them to nightmarish proportions.

Though it'd be impossible to list all the most frightening sci-fi movie creations because there's just too damn many, here are a few of the most scariest sci-fi movie monsters that have given their audiences nightmares through the decades.

11. Assimilating Alien - The Thing

Dune Sandworm
Universal Pictures

The Thing from, um, The Thing, might not be the most subtle creature on this list, but that doesn't make it any less horrifying. In fact, it's transparent visibility in the film's mind-melting gore and creature effects sequences (some of the best ever committed to celluloid) just make it all the scarier and more memorable.

An alien of ambiguous origin buried in the Antarctic ice for some 100,000 years, the Thing has the ability to infect, absorb, and mimic any living thing in comes into contact with. What's more, this mimicry is perfect, and even the person affected might not even realize what's happening. Furthermore, each individual cell of the alien is its own separate entity, meaning if it entered into a dense population, it would infect the entire world in a matter of only weeks.

If threatened, the creature has the ability to contort and mutate itself into horrifying abominations on the fly to protect itself, individual limbs and body parts sprouting eyes and legs and tendrils to escape harm. If all else fails, the various "things" can meld together into a single, giant mass fleshy mass of tentacles and deformed human features.

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Writer, student, and part time-journo in the Pacific Northwest. TWIN PEAKS was shot in my backyard.