Apocalyptic fiction is a sub-genre of science fiction (or, in some cases, the more general category speculative fiction) that is concerned with the end of civilization through nuclear war, plague, or some other general disaster. Post-apocalyptic fiction is set in a world or civilization after such a disaster. The time frame may be immediately after the catastrophe, focusing on the travails or psychology of survivors, or considerably later, often including the theme that the existence of pre-catastrophe civilization has been forgotten (or mythologized). Post-apocalyptic stories often take place in an agrarian, non-technological future world, or a world where only scattered elements of technology remain.

There is a considerable degree of blurring between this form of science fiction and that which deals with false utopias or dystopic societies. A work of apocalyptic or post-apocalyptic fiction might also be called a ruined Earth story, or dying Earth if the apocalypse is sufficiently dire.

The genres gained in popularity after World War II, when the possibility of global annihilation by nuclear weapons entered the public consciousness. However, recognizable apocalyptic novels existed at least since the first quarter of the 19th century, when Mary Shelley's The Last Man was published. Additionally, the subgenres draw on a body of apocalyptic literature, tropes, and interpretations that are millennia old.