A monster movie (creature feature or giant monster film) is a film which revolves around innocent civilians and emergency services struggling to stay alive in assaults against giant monsters. The film may also belong to the horror, fantasy or science fiction genre. In most cases, it is applied to films that feature oversized monsters. Monster movies originated with adaptations of horror folklore and literature. In Japanese cinema, such monsters are referred to as Kaiju. Typically, movie monsters differ from more traditional antagonists in that many exist due to circumstances beyond their control; their actions are not entirely based on choice, potentially making them objects of empathy to film viewers.

A monster is any creature, usually imaginary, that is considered frightening or grotesque.