Cennétig mac Lorcáin (died 951) was an Irish king. He was the father of Brian Boru, who was High King of Ireland from 1002 until his death in 1014.
In some genealogical records, he is listed as Kennedy, and his father is listed as Lorcan, due to anglicization of Gaelic names.
Cennétig was king of the Dál gCais, one of the tribes of the Déisi, subject peoples in Munster. Their name was new, first recorded in the 930s, and they had previously been an undistinguished part of the northern Déisi. The kings of Munster at this time came from the Eóganachta, a vast, complex group of kindreds who claimed descent from Eógan Már. The learned men of the Dál gCais provided a new, and improved, genealogy for their kings, tracing their descent from Eógan Már's brother Cormac Cass.
The Dál gCais were based in eastern County Clare, part of the region known as Tuadmumu (later Thomond), a name which first appears in 944 in the report of the defeat of Cennétig at Gort Rotacháin by the Eóganachta king Cellachán Caisil.
The report of Cennétig's death in 951 calls him 'king of Tuadmumu'.
Cennétig appears to have had many children, perhaps 11 sons, including Brian Boru. His daughter Órlaith was the wife of the High King of Ireland Donnchad Donn. Órlaith was killed in 941, supposedly for adultery with her stepson Óengus.
Two of his sons - Dub and Finn - are said to have died at Gort Rotacháin in 944, two - Donncuan and Echthighern - died in 950 during the invasion of Munster by Donnchad Donn's successor Congalach Cnogba. Lachtna apparently succeeded his father, but was killed soon after, and followed by his brother Mathgamain.
