Cleveland, region and former administrative county, northeastern England, along the River Tees and the North Sea. The region comprises parts of the historic counties of Durham and Yorkshire to the north and south of the Tees, respectively. It is divided administratively into the following unitary authorities: Hartlepool, Stockton-on-Tees, Middlesbrough, and Redcar and Cleveland. At the core of the region is the metropolitan area of Teesside, which incorporates the urban areas of Middlesbrough, Stockton-on-Tees, and the western portion of Redcar and Cleveland.