County Dublin (Irish: Contae Bhaile Átha Cliath or Contae Átha Cliath) is one of the thirty-two traditional counties of Ireland, located on the island's east coast, within the province of Leinster. The county is divided into the local government areas of Dublin City, Dún Laoghaire–Rathdown, Fingal and South Dublin. The latter three were counties created in 1994, when County Dublin ceased to exist for administrative purposes. The four areas are a NUTS III statistical region of Ireland (coded IE061).
Dublin is Ireland's most populous county, with over 1.345 million residents as of 2016 - approximately 27% of the Republic of Ireland's total population. Dublin city is the capital and largest city of the Republic of Ireland, as well as the largest city on the island of Ireland. Roughly 9 out of every 10 people in County Dublin lives within Dublin city and its suburbs. Several sizeable towns which are not part of the city, such as Swords, Rush, Donabate and Balbriggan, are located in the north of the county.
The third smallest county by land area, Dublin is bordered by Meath to the west and north, Kildare to the west, Wicklow to the south and the Irish Sea to the east. The southern part of the county is dominated by the Dublin Mountains, which rise to around 2,500 feet (760 m) and contain numerous valleys, reservoirs and forests. The county's east coast is punctuated by several bays and inlets, including Rogerstown Estuary, Broadmeadow Estuary, Baldoyle Bay and most prominently, Dublin Bay. The northern section of the county, today known as Fingal, varies enormously in character, from densely populated suburban towns of the city's commuter belt to flat, fertile plains, which are some of the country's largest horticultural and agricultural hubs.
Dublin is the oldest county in Ireland, and was the first part of the island to be shired following the Norman invasion in the late 1100s. While it is no longer used as an administrative division for local government, it retains a strong identity in popular culture, and Dublin continues to be referred to as both a region and county interchangeably, including at government body level.