Horror films are a film genre seeking to elicit a negative emotional reaction from viewers by playing on the audience's most primal fears. They often feature scenes that startle the viewer through the means of macabre and the supernatural, thus they may overlap with the fantasy and supernatural genre. Horrors frequently overlap with the thriller genre.

Horror films often deal with the viewer's nightmares, hidden worst fears, revulsions and terror of the unknown. Plots written within the horror genre often involve the intrusion of an evil force, event, or personage, commonly of supernatural origin, into the everyday world. Themes or elements often prevalent in typical horror films include ghosts, torture, gore, werewolves, ancient curses, satanism, demons, vicious animals, vampires, cannibals, haunted houses, zombies, sadism and serial killers. Conversely, stories of the supernatural are not necessarily always a horror movie as well.

The first depictions of supernatural events appear in several of the silent shorts created by the film pioneer Georges Méliès in the late 1890s, the best known being Le Manoir du diable (aka, The Haunted Castle, 1896) which is sometimes credited as being the first horror film. Another of his horror projects was 1898's La Caverne maudite (aka, The Cave of the Unholy One, literally "the accursed cave").Japan made early forays into the horror genre with Bake Jizo and Shinin no Sosei, both made in 1898. In 1910, Edison Studios produced the first film version of Frankenstein, which was thought lost for many years.