This article is about the prevention of flight in a region of airspace by the application or threat of military power. For information on prevention of flight ordinarily enforced by civil regulation or legal means, see Prohibited airspace.

A no-fly zone (or no-flight zone) (NFZ) is a territory or an area over which aircraft are not permitted to fly. Such zones are usually set up in a military context, somewhat like a demilitarized zone in the sky, and usually prohibit military aircraft of a belligerent power from operating in the region. Aircraft that break the no-fly zone may be shot down, depending on the terms of the NFZ.