Merseyside (/ˈmɜːrzisaɪd/ MUR-zee-syde) is a ceremonial and metropolitan county in North West England. It borders Lancashire to the north, Greater Manchester to the east, Cheshire to the south, the Welsh county of Flintshire across the Dee Estuary to the southwest, and the Irish Sea to the west. The largest settlement is the city of Liverpool.
The county is highly urbanised, with an area of 249 square miles (645 km) and a population of 1,475,541 in 2024. Liverpool is located in the centre of the county on the east bank of the Mersey Estuary, and Birkenhead opposite on the west bank. St Helens is in the east of the county, and Southport in the north. For local government purposes the county comprises five metropolitan boroughs: Knowsley, St Helens, Sefton, Wirral, and Liverpool. The borough councils, together with that of Halton in Cheshire, collaborate through the Liverpool City Region Combined Authority.