He was the son of an artisan and a lady of the Irish royal court.
Born in Connaught, Ireland, and baptized Lochan, he was educated at Kilmacahil, Kilkenny, where the monks named him Fionnbharr (white head) because of his light hair; he is also known as Bairre and Barr.
He went on pilgrimage to Rome with some of the monks, visiting St. David in Wales on the way back. Supposedly, on another visit to Rome the Pope wanted to consecrate him a bishop but was deterred by a vision, notifying the pope that God had reserved that honor to Himself, and Finbarr was consecrated from heaven and then returned to Ireland.
At any rate, he may have preached in Scotland, definitely did in southern Ireland, lived as a hermit on a small island at Lough Eiroe. The island is now called Gougane Barra (the little rock-fissure of Finnbarr). He is reputed to have built small churches in various other places, including one in Ballineadig, County Cork, called Cell na Cluaine, anglicized as Cellnaclona and sometimes referred to as Cloyne, causing it to be confused with Cloyne (Cluain Uamha) in east Cork. It was in Cell na Cluaine that, years later, he happened to die. On the river Lee, founded a monastery that developed into the city of Cork, of which he was the first bishop.
His monastery became famous in southern Ireland and attracted numerous disciples. Many extravagant miracles are attributed to him, and supposedly, the sun did not set for two weeks after he died at Cloyne about the year 633. His feast day is September 25th.