Newton Aycliffe is a town in County Durham, England. Founded in 1947 under the New Towns Act of 1946, the town is 5 miles to the north of Darlington and 10 miles to the south of Durham. It is the oldest new town in the north of England. Together with the bordering Aycliffe Village and the north part of School Aycliffe, it forms the civil parish of Great Aycliffe. The population of the town at the time of the 2021 census was 26,415.