A civilizational collapse (sometimes referred to as social collapse or societal collapse) is a  drastic decrease in human population size, or in political, economic or social complexity, across essentially the entire world, for an extended period of time. Civilizational resilience is humanity's capacity to resist, or recover from, civilizational collapse.

In Toby Ord's typology, unrecoverable civilizational collapses constitute one of the three main types of existential catastrophe (Ord 2020).