Middlesbrough, colloquially known as Boro, is a port town in the Borough of Middlesbrough, North Yorkshire, England. Lying to the south of th…Middlesbrough, colloquially known as Boro, is a port town in the Borough of Middlesbrough, North Yorkshire, England. Lying to the south of the River Tees, Middlesbrough forms part of the Teesside built-up area and the Tees Valley. With a population of 148,215 recorded in 2021.