Inlet of the South Pacific Ocean, New South Wales, southeastern Australia. It is one of the world's finest natural harbours. It was sighted in 1770 by Capt. James Cook. Its entrance is between North and South Heads, where naval and military stations are located. Sydney is on its southern shore and the northern suburbs of Sydney are on its northern shore; the shores are joined by the Sydney Harbour Bridge, which was built in 1932.