Stockton-on-Tees, often simply referred to as Stockton, is a market town in the Stockton-on-Tees unitary authority borough of County Durham, England. With a population of 84,815 in the 2021 UK census. It is part of the Teesside and the devolved Tees Valley area, on the northern banks of the River Tees. The Tees was straightened in the early 1800s for larger ships to access the town.