St. Carthage came to Lismore in 635 with a group of 500 monks. He established his monastic church on the site of the present cathedral. There has been a consecrated building on this site since 635. A stone church was built in the mid twelfth century but probably burned down in a big fire that swept through Lismore in 1207. It was rebuilt soon afterwards in its present form, but destroyed 400 years later in 1600, during a rebellion against the British. Richard Boyle, of Lismore Castle, pledged to rebuild the Cathedral. In 1827, the Tower and Spire were added in neo-gothic style.
Located about 5 miles north of Cappoquin, Mount Melleray Abbey is a Cistercian Abbey founded in 1932 by a group of Irish monks. It is a fully functional monastery and is open to visitors.