Science fiction film is a film genre that uses speculative, science-based depictions of imaginary phenomena such as extra-terrestrial lifeforms, alien worlds, and time travel, often along with technological elements such as futuristic spacecraft, robots, or other technologies. Science fiction films have often been used to provide social commentary on political or social issues, and to explore philosophical issues, such as "what makes us human." In many cases, tropes derived from written science fiction may be used by filmmakers ignorant of or at best indifferent to the standards of scientific plausibility and plot logic to which written science fiction is traditionally held.

The genre has existed since the early years of silent cinema, when Georges Melies' A Trip to the Moon (1902) amazed audiences with its trick photography effects. From the 1930s to the 1950s, the genre consisted mainly of low-budget B-movies. After Stanley Kubrick's 1968 landmark 2001: A Space Odyssey, the science fiction film genre was taken more seriously. In the late 1970s, big-budget science fiction films filled with special effects became popular with audiences. The hugely influential Star Wars trilogy and Close Encounters of the Third Kind appeared, paving the way for the blockbuster hits of subsequent decades, such as E.T. the Extra Terrestrial (1982) and Men in Black (1997).