Lismore Abbey is a former monastery in Lismore, County Waterford, Ireland, reportedly in its day the most celebrated in the South of Ireland. Its site is now occupied by Lismore Castle. It was founded in the year 635 by St Mochuda, also known as St. Carthage, in a picturesque site, steeply rising from the southern bank of the River Blackwater. Its founder had spent nearly forty years of his monastic life in the monastery of Rahan on the southern borders of ancient Meath. In 635 Prince Blathmac, son of Aedh Slaine, of the southern Hy Mall, evicted him, and he moved to Lismore, on the edge of what was then called Avonmore, "the great river", a site granted to St. Carthage by the prince of the Desii of Waterford. Lismore was founded in 635; Mochuda died two years later.