section of the southwestern Pacific Ocean, between the southeastern coast of Australia and Tasmania on the west and New Zealand on the east; it merges with the Coral Sea to the north and encloses a body of water about 1,400 miles (2,250 km) wide and 900,000 square miles (2,300,000 square km) in area. Bass Strait (between Tasmania and Australia) leads southwest to the Indian Ocean, and Cook Strait (between North and South islands, New Zealand) leads east to the Pacific.

The sea was named for the Dutch navigator Abel Tasman (Tasman, Abel Janszoon), who navigated it in 1642. Its New Zealand and Australian shorelines were explored in the 1770s by the British mariner Captain James Cook and others. With maximum depth exceeding 17,000 feet (5,200 m), the seafloor's most distinctive feature is the Tasman Basin. The South Equatorial Current and trade wind drift feed the southerly moving East Australian Current, which is the dominant influence along the Australian coast. From July to December its effect is minimal, and colder waters from the south may penetrate as far north as latitude 32° S. Lord Howe Island, situated at this parallel, represents the most southerly development of a modern coral reef. In the eastern Tasman Sea, surface circulation is controlled by a stream from the western Pacific from January to June and by colder sub-Antarctic water moving north through Cook Strait from July to December. These various currents tend to make the southern Tasman Sea generally temperate in climate and the northern subtropical. Lying in the belt of westerly winds known as the “roaring forties,” the sea is noted for its storminess. The sea is crossed by shipping lanes between New Zealand and southeastern Australia and Tasmania, and its economic resources include fisheries and petroleum deposits in the Gippsland Basin at the eastern end of Bass Strait.