A failed state is a state that has lost its effective ability to govern its populace. A failed state maintains legal sovereignty but experiences a breakdown in political power, law enforcement, and civil society, leading to a state of near-anarchy.

Common characteristics of a failing state include a government unable to tax and police its populace, control its territory, fill political or civil offices, or maintain its infrastructure. When this happens, widespread corruption and criminality, the intervention of state and non-state actors, the appearance of refugees and the involuntary movement of populations, sharp economic decline, and military intervention from both within and without the state in question can occur.

Metrics have been developed to describe the level of governance of states. The precise level of government control required to avoid being considered a failed state varies considerably amongst authorities. Furthermore, the declaration that a state has "failed" is generally controversial and, when made authoritatively, may carry significant geopolitical consequences.