South Dublin is a county in Ireland, within the province of Leinster and the Eastern and Midland Region. It is one of three successor counties to County Dublin, which was disestablished for administrative purposes in 1994. South Dublin County Council is the local authority for the county. The county contains both dense suburbs of Dublin and stretches of unpopulated mountains. In 2022 it had a population of 301,705, making it the fourth most populous county in the state.

County Dublin is a county in Ireland, and holds its capital city, Dublin. It is located on the island's east coast, within the province of Leinster. Until 1994, County Dublin was a single local government area; in that year, the county council was divided into three new administrative counties: Dún Laoghaire–Rathdown, Fingal and South Dublin. The three administrative counties together with Dublin City proper form a NUTS III statistical region of Ireland. County Dublin remains a single administrative unit for the purposes of the courts and Dublin County combined with Dublin City forms the Judicial County of Dublin, including Dublin Circuit Court, the Dublin County Registrar and the Dublin Metropolitan District Court). Dublin also sees law enforcement and fire services administered county-wide.