Teesdale is a dale, or valley, of the east side of the Pennines in England. Its principal villages include Middleton-in-Teesdale, Mickleton, Eggleston, Romaldkirk, and Cotherstone. It gives its name to the Teesdale district of County Durham, although the south side of Teesdale is traditionally part of the North Riding of Yorkshire. Formerly the Startforth Rural District, it was transferred to County Durham for administrative and ceremonial purposes on 1 April 1974, under the provisions of the Local Government Act 1972.

The River Tees flows through Teesdale before reaching Barnard Castle and then passing to the south of Darlington, reaching the North Sea south of Hartlepool after passing Stockton-on-Tees and Middlesbrough. Running roughly parallel to Teesdale to the north is Weardale.