East River, a tidal strait in New York City, connecting Upper New York Bay and Long Island Sound. The strait is 16 miles (26 km) long and some 600 to 4,000 feet (180 to 1,220 m) wide. It separates Manhattan and Bronx boroughs from Brooklyn and Queens boroughs on Long Island. The East River is connected with the Hudson River by the Harlem River at the north end of Manhattan. In the East River are Roosevelt, Wards, Randalls, and Rikers islands. The strait is crossed by numerous bridges, including the Brooklyn Bridge. Several tunnels run beneath it.