coast guard, a force, usually naval, that enforces a country’s maritime laws and assists vessels wrecked or in distress on or near its coasts. Such forces originated during the early 19th century as a restraint on smuggling.

A coast guard may also be responsible for the maintenance of lighthouses, buoys, and other navigational aids and for administering emergency aid to merchant seamen and to victims of natural disasters, such as floods and hurricanes. In some countries coast guard duties include icebreaking in inland waterways and the collection and dissemination of meteorological data pertaining to floods, hurricanes, and storms. The International Ice Patrol, operated by the U.S. Coast Guard, maintains surveillance of icebergs in the North Atlantic shipping lanes.

Nearly all coastal countries have some form of coast guard. Among the best known are the U.S. Coast Guard, the Coastguard Service in Britain, the Canadian Coast Guard, and the Japan Coast Guard. All are under the supervision of their respective governments. In several European countries, coast guard duties are performed by volunteer lifeboat associations.