Birmingham is a city and metropolitan borough in the metropolitan county of West Midlands in England. It is the second-largest city in Britain â commonly referred to as the second city of the United Kingdom â with a population of 1.145 million in the city proper. Birmingham borders the Black Country to its west and, together with the city of Wolverhampton and towns including Dudley and Solihull, forms the West Midlands conurbation. The wider metropolitan area has a population of 4.3 million, making it the largest outside of London.