seaport and unitary authority, geographic and historic county of Durham, northeastern England, on the North Sea.

The old town, occupying a limestone peninsula that sheltered a fishing harbour on the North Sea coast, enjoyed the patronage of the medieval prince-bishops of Durham, who granted its charter of 1201. Modern development dates from the coming of the railway in 1835, when Hartlepool became a port for the Durham coalfield, exporting coal and importing pit props. In 1847 the West Hartlepool dock was added, and a new town was laid out alongside. It grew rapidly with iron and steel, shipbuilding, and marine engineering industries.

As those industries have declined, Hartlepool has come to depend increasingly upon its association with Teesside. The port is now concerned mainly with servicing North Sea petroleum fields, and the town has a chemical industry. A nuclear power station stands at Seaton Carew in the southeast, and light industries have been established northwest of the town. Area 36 sq mi (94 sq km). Pop. (2005 est.) 90,000.