unitary authority, geographic county of North Yorkshire, historic county of Yorkshire, England. It lies on the south side of the River Tees between Middlesbrough and the rocky coastline and stretches southeastward along the coast past the highest cliffs of England, at Boulby, which stand more than 600 feet (180 metres) above the North Sea. It also extends inland to cover the northernmost, heavily wooded section of the Cleveland Hills.

The unitary authority's northwestern portion along the Tees estuary, including the towns of Eston, South Bank, Grangetown, Lackenby, and Redcar, is the most heavily industrialized part of the Teesside metropolitan area. It includes modern steelworks (at Lackenby and Redcar), petrochemical plants, and other manufacturing facilities. The reclaimed mudflats of the Tees estuary below Middlesbrough provide spacious sites for industrial and port installations, which include an oil refinery and the international port of Teesport. A direct pipeline supplies offshore North Sea oil to the refinery.

The south and east of the unitary authority is a scenic and largely rural area. The coastal resort of Saltburn-by-the-Sea and the inland market town of Guisborough are favoured residential towns. Guisborough also has been a centre of office development. In the south Redcar and Cleveland extends into the North York Moors National Park. Area 95 square miles (245 square km). Pop. (2005 est.) 138,600.