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 roughly rectangular peninsula is about 15 miles (24 km) long and 7 miles (11 km) wide. Historically, the Wirral was wholly within Cheshire; in the Domesday Book, its border with the rest of the county was placed at "two arrow falls from Chester city walls." However, since the passing of the Local Government Act 1972, only the southern third has been in Cheshire, with the rest in metropolitan borough in the modern county of Merseyside.
The Wirral contains both affluent and deprived areas, the former largely in the west, south and north coast of the peninsula, and the latter concentrated in the east, around the built-up district of Birkenhead.
The name Wirral literally means "myrtle corner", from the Old English wir, a myrtle tree, and heal, an angle, corner or slope. It is supposed that the land was once overgrown with bog myrtle, a plant no longer found in the area, but plentiful around Formby, to which the Wirral would once have had a similar habitat. The name was given to the Hundred of Wirral (or Wilaveston) around the 8th century.