Celtic saint, monastic founder, abbot, and hero of legendary voyages in the Atlantic Ocean. Reputedly raised and educated by Abbess St. Ita at her boys' school in what later became County Limerick, he later studied under Abbot St. Jarlath of Tuam. After becoming a monk and priest, he was entrusted with the abbey of Ardfert and subsequently established monasteries in Ireland and Scotland, the chief one being Clúain Ferta Brénaind (Anglicized Clonfert), founded in 561. He is called Brendan of Clonfert to distinguish him from several namesakes.

A noted traveler, Brendan voyaged to the Hebrides (according to St. Adamnan's life of Abbot St. Columba of Iona) and to western Scotland and perhaps to Wales and Brittany. Later, possibly as early as the 8th century, Brendan was immortalized as the hero of a legendary Christian tale of sea adventure, Navigatio Brendani (“Voyage of Brendan”). This Irish epic, a narrative masterpiece, was translated into Latin prose early in the 10th century. According to the Navigatio, Brendan makes an astonishing Atlantic journey with other monks to the “Promised Land of the Saints” (later identified possibly as the Canary Islands), which he reaches after a prolonged search. St. Brendan's Island, somewhere in the Atlantic and long sought by sailors, was believed in Columbus' time to have been sighted by inhabitants of the Azores, probably the effect of mirage.