Dún Laoghaire (dōn lărˈē, dŭn lârˈə) [key], city (1991 pop. 55,540), Co. Dublin, E central Republic of Ireland, on the Irish Sea. It is the main passenger and mail port for Dublin and a seaside resort with yachting and fishing. With the opening of a railroad to Dublin in 1834 and the completion of the port in 1859, Dún Laoghaire grew rapidly. The city was known as Kingstown before 1921 and as Dunleary before 1821. Dún Laoghaire is connected to Holyhead, Wales by passenger and car ferry.