Dún Laoghaire is a suburban coastal town on the south side of Dublin, Ireland, in the province of Leinster. It serves as the administrative centre of the county of Dún Laoghaire–Rathdown.
The town was built up alongside a small existing settlement following legislation passed in 1816 that allowed the construction of a major port to serve Dublin. It was known in English as Dunleary until it was renamed Kingstown in honour of George IV's visit in 1821; in 1920 it was given its present name, which is the original Irish form from which "Dunleary" was anglicised.
Over time, Dún Laoghaire became a residential location and a seaside resort. It was the terminus of Ireland's first railway and became the administrative centre of the former borough of Dún Laoghaire, and from 1994 of the county of Dún Laoghaire–Rathdown.