A depth charge is an anti-submarine warfare (ASW) weapon. It is intended to destroy a submarine by being dropped into the water nearby and detonating, subjecting the target to a powerful and destructive hydraulic shock. Most depth charges use high explosive charges and a fuze set to detonate the charge, typically at a specific depth. Depth charges can be dropped by ships, patrol aircraft, and helicopters.
Depth charges were developed during World War I, and were one of the first effective methods of attacking a submarine underwater. They were widely used in World War I and World War II. They remained part of the anti-submarine arsenals of many navies during the Cold War. Depth charges have now largely been replaced by anti-submarine homing torpedoes.
A depth charge fitted with a nuclear warhead is also known as a "nuclear depth bomb". These were designed to be dropped from a patrol plane or deployed by an anti-submarine missile from a surface ship, or another submarine, located a safe distance away. By the late 1990s all nuclear anti-submarine weapons had been withdrawn from service by the United States, the United Kingdom, France, Russia and China. They have been replaced by conventional weapons whose accuracy and range had improved greatly as ASW technology improved.