Long Island Sound, body of salt water, northeastern United States, bounded on the north by Connecticut and on the south by Long Island, New York. The eastern end of the sound is connected with the Atlantic Ocean by Gardiners Bay and Block Island Sound; at the western end the East River connects the sound with New York Bay. The sound is 180 km (110 mi) long, from 16 to 40 km (from 10 to 25 mi) wide, and covers 3,400 sq km (1,300 sq mi). Among the many rivers flowing into it are the Connecticut, the Thames, and the Housatonic. The sound has excellent fisheries; it is also a coastal shipping route serving the Connecticut ports of New Haven, New London, and Bridgeport.