Merseyside (pronounced /ˈmɝːzisaɪd/) is a metropolitan county in North West England, with a population of 1,365,900. Taking its name from the River Mersey, the title "Merseyside" came into existence as a metropolitan county in 1974, after the passage of the Local Government Act 1972, and the county consists of five metropolitan boroughs adjoining the Mersey Estuary, including the City of Liverpool.
Merseyside County Council was abolished in 1986, and so its districts (the metropolitan boroughs) are now effectively unitary authorities. However, the metropolitan county continues to exist in law and as a geographic frame of reference.
Merseyside is divided into two parts by the Mersey Estuary: the Metropolitan Borough of Wirral is located to the west of the estuary on the Wirral Peninsula; the rest of the county is located on the eastern side of the estuary. The eastern boroughs of Merseyside border Lancashire to the north and Greater Manchester to the east, and both parts of Merseyside, west and east of the estuary, border Cheshire to the south.
The territory comprising the county of Merseyside previously consisted of the county boroughs of Birkenhead, Wallasey, Liverpool, Bootle, Southport and St Helens. Birkenhead and Wallasey were part of the administrative county of Cheshire, whilst Liverpool, Bootle, Southport and St Helens were part of the administrative county of Lancashire.