Cormac mac Airt (son of Art), also known as Cormac ua Cuinn (grandson of Conn) or Cormac Ulfada (long beard), was, according to medieval Irish legend and historical tradition, a High King of Ireland. He is probably the most famous of the ancient High Kings, and may have been an authentic historical figure, although many legends have attached themselves to him, and his reign is variously dated as early as the 2nd century and as late as the 4th. He is said to have ruled from Tara, the seat of the High Kings of Ireland, for forty years, and under his rule Tara flourished. He was famous for his wise, true, and generous judgments. In the Annals of Clonmacnoise, translated in 1627, he is described as:
The hero Fionn mac Cumhaill is supposed to have lived in Cormac's time, and most of the stories of the Fenian Cycle are set during his reign.