POST-APOCALYPTIC science 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 Utopian or Dystopian 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.