County Dublin (Irish: Contae Bhaile Átha Cliath), or more correctly today the Dublin Region[1] (Réigiúin Átha Cliath), is the area that contains the city of Dublin, the capital and largest city of the Republic of Ireland as well as the largest city on the island of Ireland; and the modern counties of Dun Laoghaire-Rathdown, Fingal and South Dublin. The Dublin Regional Authority is the regional authority for the region. Dublin was one of the oldest of the Counties of Ireland to be formally structured.

source: Wikipedia County Dublin