Flannán mac Toirrdelbaig (Latin: Flannanus; fl.
640)[1] was an Irish saint who lived in the 7th century and was the son of an Irish chieftain, Toirdhealbhach of Dál gCais.
He entered Mo Lua's monastery at Killaloe, where it is believed he became an Abbot.
He made a pilgrimage to Rome where Pope John IV consecrated him as the first Bishop of Killaloe, of which he is the Patron Saint.
His feast day is 18 December.