Stockton-on-Tees is a market town in County Durham, England, with a population of 84,815 at the 2021 UK census. It gives its name to and is the largest settlement in the wider Borough of Stockton-on-Tees. It is part of Teesside and the Tees Valley, on the northern bank of the River Tees. The Tees was straightened in the early 19th century for larger ships to access the town.