AFI described science fiction as "a genre that marries a scientific or technological premise with imaginative speculation. Whether it's a flying saucer whirling through space or a gleaming city on a distant planet, at the core of all science fiction is the provocative question, "What if...?" Science fiction presents stories and situations that tap our brightest hopes and darkest fears about what might, one day, turn out to be true."

Nominees: 22 of the 50 movies contained an alien presence.

Winners: 2001: A Space Odyssey (1968) (# 1), Star Wars: Episode IV - A New Hope (1977) (# 2), E.T. - The Extra Terrestrial (1982) (# 3), A Clockwork Orange (1971) (# 4), The Day The Earth Stood Still (1951) (# 5), Blade Runner (1982) (# 6), Alien (1979) (# 7), Terminator 2: Judgment Day (1991) (# 8), Invasion of the Body Snatchers (1956) (# 9), Back to the Future (1985) (# 10).

Comments: Eternal Sunshine of the Spotless Mind (2004) was a romantic comedy, for the most part, not Science Fiction. Planet of the Apes (1968) and Close Encounters of the Third Kind (1977) should be in the top 10, as well as The Matrix (1999). E.T. - The Extra-Terrestrial (1982) was more a children's fantasy film, not pure science fiction. Terminator 2: Judgment Day (1991), although it had science-fiction elements, was mostly an action film. Dark City (1998) should have been a nominee. Back to the Future (1985) was a light-hearted comedy for the most part, although it had time-travel/sci-fi elements.