Ruadán (d. 584), abbot of Lorrha and saint in the Irish tradition, was son of Fergus Bern, son of Dera Dub of the Uí Duach in Osraige, and a descendant of the kings of Munster. Many aspects of the traditions relating to him are quite unhistorical. His Latin and Irish Lives make him a pupil of St Finnian (qv) (d. 549) of Clonard from whom he received holy orders. He is also brought into contact with other sixth-century figures, such as Diarmait (qv) (d. 565) son of Cerball, king of Tara, St Brendan (qv) (d. 577/83) of Clonfert, and Colum Cille (qv) (d. 597). He is named among the ‘twelve apostles of Ireland’, the reputed disciples of Finnian of Clonard. His first monastic foundation was in Ara Mac Ua Néitt in Muscraige Tíre (to the north-east of Lough Derg, on the River Shannon). His principal monastic foundation was at Lothra (Lorrha, Co. Tipperary), in the same area, but his activities extended throughout Ireland. Lothra became a famous and populous monastery; it is said that at one time it had 150 monks.
He was, it seems, by nature a quarrelsome man. A poem attributed to Cuimmín of Condere (Connor, Co. Antrim) on the characteristics of the saints of Ireland says of Ruadán ‘he loved cursing’. There are accounts of disputes with Brendan of Clonfert, who was forced to abandon a site at Tulach Bréndan because it was too close to Lothra. Another tale recalls a deputation from the saints of Ireland to Ruadán which upbraided him and his community for their indolent lifestyle, as they subsisted upon the nourishing sap of a magic tree without having to cultivate the soil. His Life gives a mythical account of his cursing of Diarmait son of Cerball for his capture of Áed Guaire, king of Uí Maine, who had taken refuge with Ruadán. The saint and his clerics proceeded to Tara, where they underwent a public fast (troscad) against Diarmait, pouring imprecations and curses upon his head. Diarmait in turn fasted against Ruadán, till he was tricked by him into believing that he and his clerics had ended their fast. It has been plausibly suggested that the story was invented to account for the official adoption of Christianity by the kings of Tara in the sixth century. These and other stories in his Lives convey very little factual information about the historical Ruadán, who remains a shadowy figure. His obit appears only in the Annals of Tigernach (Tigernach Ua Bráein (qv)); he is commemorated on 15 April in all the Irish marytrologies.