Knocklyon is a suburb of Dublin in county of South Dublin, within the old County Dublin, Ireland. Unlike many Dublin suburbs, Knocklyon was not developed around a village; rather it largely comprises modern housing but a number of old cottages and farmhouses along Knocklyon Road attest to the area's rural past.

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.