Fort Sullivan (briefly Fort Sherbrooke) was a 19th-century military fortification in Eastport, Maine. It lay opposite New Brunswick, Canada, and served as an important coastal defense for the easternmost United States of America during the 19th century. As part of the establishment of New Ireland during the War of 1812, British Commodore Sir Thomas Hardy, 1st Baronet conquered the fort in 1814 and renamed it Fort Sherbrooke after John Coape Sherbrooke, the Governor of Nova Scotia.