Saint Muiredach mac Echdach, also known as Murtagh, was the founding bishop of the Diocese of Killala, Killala, Ireland in the 6th century.
He was placed at the head of the church by St. Patrick, patron saint of Ireland. He allegedly met with St. Columba in the year 575, in a town called Ballysadare. He was connected to the royal family of King Lóegaire mac Néill. He probably resigned after a few years, and retired to an island off the Sligo coast in Donegal Bay.
The uninhabited island, Inishmurray, bears his name. He may also be the patron of the monastery that was on that island. He died there as a hermit, and his feast day is August 12.
"Killala". Catholic Encyclopedia. New York: Robert Appleton Company. 1913. http://www.newadvent.org/cathen/08640a.htm.