Offshore radio refers to the practice of radio broadcasting from ships or fixed maritime structures, usually in international waters. The claimed first wireless broadcast of music and speech for the purpose of entertainment was transmitted from a Royal Naval craft, the HMS Andromeda, in 1907. The broadcast was organized by a Lieutenant Quentin Crauford using the callsign QFP while the ship was anchored off Chatham in the Thames Estuary, England. The majority of offshore broadcasters have however been pirate radio stations using seaborne broadcasting as a means to circumvent national broadcasting regulations, for example the practice has been used by broadcasting organisations like the Voice of America as a means of circumventing national broadcasting regulations of other nations.

Offshore pirate stations have operated off the coasts of Belgium, Denmark, Israel, The Netherlands, New Zealand, Sweden, The United Kingdom and even (on rare occasions) The United States. See Pirate radio for full details.