Gustavus Conyngham, Irish-born American merchant sea captain, an officer in the Continental Navy and a privateer.

Gustavus Conyngham (about 1747 – 27 November 1819) was an Irish-born American merchant sea captain, an officer in the Continental Navy and a privateer. As a commissioned captain fighting the British in the American Revolutionary War, he captured 24 ships in the eastern Atlantic between May 1777 and May 1778, bringing the expenses associated with British shipping to a then all-time high. He has been called "the most successful of all Continental Navy captains".