The Church of Ireland Cathedral is named after Saint Canice, who also gave his name to the town. The 13th century cathedral of St. Canice is the second longest cathedral in Ireland. The site on which the cathedral stands has been a site of Christian worship since the 6th century. The earliest church on the site is presumed to have been made of wood, being replaced eventually in the later medieval period by a romanesque-style stone church. This was in turn replaced by the current imposing medieval cathedral.

The cathedral contains some of the finest 16th century monuments in Ireland. The memorials stretch right across the social spectrum from the great figures of the house of Ormonde to the humble shoemaker and carpenter. The baptismal font is original and the ancient stone of enthronement for bishops still exists under the seat of the medieval throne in the North Transept, where to this day the bishops of Ossory are enthroned. There are continental carvings on the choir stalls and a hammerbeam roof.