Selby is a market town and civil parish in North Yorkshire, England; it is located 12 miles south of York on the River Ouse. In the 2021 UK Ce…Selby is a market town and civil parish in North Yorkshire, England; it is located 12 miles south of York on the River Ouse. In the 2021 UK Census, it had a population recorded at 19,760. The town was historically part of the West Riding of Yorkshire; from 1974 until 2023, the town was the administrative centre of the Selby District.