The science fiction film genre is filled with many films that purport to be scary monster alien movies, but often the aliens aren't even scary enough to qualify as monsters. Not so with the films on this list of scary monster alien movies. These aliens are grotesque, horrifying, and out for human blood. These scary monster alien movies will make you not want to believe there is life from other planets.

  1. "Alien" - A claustrophobic psychological thriller set on the spaceship Nostromo, "Alien" finds Sigourney Weaver, along with a crew of other space explorers, trapped on the ship with a grotesque beast born from one of their fellow crew members' chest. As it grows to full size from the tiny beast that exploded out of the man's torso, it hunts down the crew one by one, until only Weaver is left to battle it, alone in space with nothing but her wits. This terrifying film should top any list of scary monster alien movies.

  2. "Aliens" - The sequel to the first "Alien" takes a different tack. Instead of one alien, there are many, including a massive egg-laying queen, and this time Weaver is teamed with a group of space marines, with the firepower to take the aliens on. Though it is more an action film than the original's psychological thriller, it still packs quite a few scares, making it a logical choice for fans of scary monster alien movies.

  3. "Predator" - This time, the scary monster, an extraterrestrial hunter, is on earth, in the jungles of South America. A group of elite commandos led by Arnold Schwarzenegger takes on this alien hunter, with bloody results. A formidable beast, this "Predator" helps to define scary monster alien movies.

  4. "Starship Troopers" - Though the film itself is more of a satire than a straight-up action film, parodying army recruiting films and corrupt media influence, its alien bugs come in a variety of scary shapes and sizes. This is a scary monster alien movie with wit and a message on top of blood, guts, and a welcome splash of T&A.

  5. "John Carpenter's The Thing" - The inhabitants of a remote Alaskan outpost are tormented by a shape-shifting alien being in this final entry on our list of scary monster alien movies. Any film in which a man's disembodied head turns into a spider is enough to gross out even the most jaded fans of scary monster alien movies.