The Cenél Conaill, or "kindred of Conall", are a branch of the Northern Uí Néill, who claim descent from Conall Gulban, son of Niall of the Nine Hostages, and allegedly the first Irish nobleman to convert to Christianity. Their kingdom was known as Tír Conaill, with their powerbase at Mag Ithe in the Finn valley, however they gradually expanded to cover what is now counties Donegal and Fermanagh. The Cenél Conaill clashed regularly with their kin the Cenél nEogain, eventually capturing the latters original power-base of Ailech in the Inishowen peninsula—in modern-day County Donegal—by the 12th century.
Below is a list of their principle clans and septs.
The Cenél Luighdech (more commonly known as Sil Lugdach) descend from Lugaid mac Sétnai, the great-grandson of Conall Gulban. Their tribal territory extended from Dobhar (Gweedore) to the river Suilidhe (Swilly) in County Donegal. The O'Donnells and O'Dohertys who descend from this branch, were the two principal and most powerful septs of the Cenél Conaill. The most famous descendant of the Cenél Conaill is Saint Columba, who founded the monastery at Derry, and is claimed as being the grandson of Conall Gulban.
The Clann Chindfaoladh are a branch of the Cenél Luighdech and take their name from Cindfhealadh, the great-grandfather of Baighill, the eponym of this clans leading sept, the Ó Baoighill's (O'Boyle). The Ó Baoighill were chieftains of Tír Ainmireach and Tír Boghaine in southern Donegal, with territory originally extending from Donegal town to near Kilmacreannan along the west coast. The barony of Boylagh is alleged to take its name from the O'Boyles. By the 13th century, the O'Donnells would see the O'Boyle territory divided in two; Tír Ainmireach in the south and the Three Tuatha in the north.
The Clann Dálaigh (also Síl Dálaigh), or Clan Daly, is another name for the Ó Domhnaill sept of the Cenél Luighdech. This clan takes its name from Dálach, the father of Éicnechán, a chieftain of the Cenél Luighdech.