South Dublin is a county located in the Leinster province and the Eastern and Midland Region of Ireland. It was established as one of three successor counties following the disestablishment of County Dublin for administrative purposes in 1994. The local authority for the area is the South Dublin County Council.
The county is characterized by a diverse geography that includes both dense suburbs of Dublin and stretches of unpopulated mountains. As of 2022, it had a population of 301,075, making it the fourth most populous county in the state.