LISMORE, an ancient town of Ireland, county of Waterford, on the right bank of the Blackwater, 30 miles N.E. by E. of Cork, and communicating with Youghal by canal and the Blackwater. It stands on an elevation overlooking the river, having on the E. the cathedral, an elegant building with a tower and spire, and on a rocky precipice on the W. the massive old castle. The Blackwater is here crossed by a fine bridge, the centre arch of which has a span of 100 feet. Its chief buildings, besides the above-named, are,—a Roman Catholic chapel, a Presbyterian place of worship, a classical and other schools, a fever hospital, and several alms-houses in behalf of aged Protestant soldiers. Trade is here confined to the agricultural produce of the district, and slates from neighbouring quarries. Lismore is said to have originated from a monastery founded here by St Carthagh in the seventh century. Two centuries later it was several times pillaged by the Danes. In the thirteenth century King John of England founded the castle which, with the town, suffered much during the rebellion of 1641. From that time the town long continued in a state of decay, until it became the property of the Devonshire family, when great improvements were made. The castle is now in complete repair. Pop. (1851) 2340.