Birkenhead (/ˌbɜːkənˈhɛd/) is an industrial port town in the Metropolitan Borough of Wirral, Merseyside, England. The town is on the Wirral Peninsula, along the west bank of the River Mersey, opposite Liverpool. It lies within the historic county boundaries of Cheshire, and became part of Merseyside in 1974. At the 2021 census, the built up area as defined by the Office for National Statistics had a population of 109,835.
Birkenhead Priory and the Mersey Ferry were established in the 12th century. In the 19th century, Birkenhead expanded greatly as a consequence of the Industrial Revolution, leading to a shipbuilding firm which became Cammell Laird. A seaport was established. As the town grew, Birkenhead Park and Hamilton Square were laid out. The first street tramway in Britain was built, followed by the Mersey Railway which connected Birkenhead and Liverpool through the world's first railway tunnel beneath a tidal estuary.