Wirral or the Wirral (/ˈwɪrəl/) is a peninsula in northwest England. It is bounded to the west by the River Dee, forming a boundary with Wales, to the east by the River Mersey, and to the north by the Irish Sea. The Wirral contains both affluent and deprived areas, the former largely in the west and south of the peninsula, and the latter concentrated in the northeast, around the built-up district of Birkenhead.