Choosing the 10 worst sci-fi movies ever is a tall task, since the sheer number of bad and truly bad science fiction films continues to grow every year. What qualifies a film to be listed among the 10 worst sci-fi movies of all time usually boils down to laughably bad acting, special effects and/or writing. In most of the awful science fiction movies listed below, most of those factors are in play.

  1. "Starship Invasions." One of the first post-Star Wars movies to emerge in the late 70's, this clunker featured Robert Vaughn and Christopher Lee and told the story of a dying planet's survivors seeking to colonize Earth.

  2. "Plan 9 from Outer Space." Directed by notorious hack Ed Wood, this movies has been called "The Worst Movie Ever Made" by The Golden Turkey Awards. Try watching a few minutes of it and you'll see why.

  3. "Santa Claus Conquers the Martians." Riding the wave of cheesy sci-fi movies from the 1950's and early 1960's, this 1964 movie imagines what would happen if Martians kidnapped Santa to help make Martian kids as happy as their Earthling counterparts.

  4. "Battlefield Earth." John Travolta produced and starred in the 2000 adaptation of Scientology founder L. Ron Hubbard's most famous novel. It's bad in so many ways, from the performances down to the painful-to-hear dialogue to the goofy makeup and effects.

  5. "The Postman." Unlike the excellent David Brin novel upon which the movie is based, the film version of "The Postman" was completely lacking in irony and wit. Director and star Kevin Costner played the whole thing straight and it just didn't work at all. Costner deserves credit for effort, but the final result was long, dull and largely forgettable.

  6. "The Adventures of Pluto Nash." This 2002 Eddie Murphy sci-fi comedy is among the biggest bombs in Hollywood history, having cost an estimated $100 million and earned less than $8 million at the box office.

  7. "Highlander II: The Quickening." This was a major disappointment, given the popularity and relative quality of the original "Highlander." The sequel lacked a decent plot, worse special effects and was one of the more obvious efforts in movie history to cash in with a poorly executed sequel.

  8. "A.I." With the involvement of Stanley Kubrick and Steven Spielberg, you'd think this film would be among the best, not the worst sci-fi films ever. Think again. The ending is brutal. Of all the films on this list, "A.I." probably has the biggest share of ardent fans and harsh critics.

  9. "Star Trek: The Motion Picture." Long and boring, yet somehow it didn't kill the franchise. Considering how much more entertaining the next three movies were, this original "Star Trek" feature film looks even lamer.

  10. "The Happening." M. Night Shyamalan and his wacky plot twists finally hit the skids in this 2008 dud. Mark Wahlberg and the always-cute Zooey Deschanel have zero chemistry and the acting, plotting and pacing just make it almost unwatchable for about the final two thirds of the movie.