If all it did was to launch a franchise centered on Sigourney Weaver’s fierce survivor (still among the toughest action heroines of cinema), Ridley Scott’s claustrophobic, deliberately paced sci-fi-horror classic would still be cemented in the film canon. But Alien claims masterpiece status with its subversive gender politics (this is a movie that impregnates men), its shocking chestburster centerpiece and industrial designer H.R. Giger’s strangely elegant double-jawed creature, a nightmarish vision of hostility—and one of cinema’s most unforgettable pieces of pure craft.