Exterior of St. Laserian's Church of Ireland Cathedral in Old Leighlin in County Carlow

St. Laserian's Church of Ireland is a Church of Ireland (Anglican) Cathedral located in the village of Old Leighlin in County Carlow.
It is located at the site of a monastery founded by St Gobhan early in the seventh century; he moved on and left the monastery under the direction of his brother, St. Laserian (also known as St. Molaise). In 630, it was the location of a synod, where St Laisrén convinced a group of Irish bishops to relinquish the Celtic method of calculating the date of Easter for the Roman one.The original monastic buildings were probably made of wood and were destroyed by fire around 1060. Leighlin was named as one of five bishoprics of Leinster at the Synod of Ráth Breasail in 1111.
The present Cathedral building was begun by Donat O'Kelly or Donatus, Bishop of Leighlin from around 1152 to 1181 and was finished by the end of the 13th century with the completion of the nave and choir. The two transepts, a tower, and a chapel attached to the choir were added in the 16th century, the latter two occurred in the time of Matthew Sanders, Bishop of Leghlin from 1529 to 1549. The south transept was later demolished, and the north transept left roofless. A pipe organ was installed under the tower in 1800 and later moved to an alcove. General restorations occurred in the 19th century, including a fine timber ceiling in the chancel, installed in 1890.
Old Leighlin ceased being a Church of Ireland bishopric in 1597 during the same century it became Protestant. It merged with the Bishopric of Ferns in 1597 and is now one of Six Cathedrals in the Dioceses of Cashel, Ferns and Ossory. St. Laserian's Church of Ireland Cathedral is one of four churches in Leighlin Union of Parishes in the Dioceses of Cashel, Ferns and Ossory.