List of Irish clans in Ulster

Niall of the Nine Hostages had seven sons, two of which, Owen (Eoghan) and Conall Gulban (Conaill) traveled north from the over-kingdom of Connacht and into the northern and western regions of the over-kingdom of Ulster, an area equivalent to modern-day County Donegal.

These two became the progenitors of the two Cenél's (or kindreds) that would make up the Northern Uí Néill; the Cenél Eóghain based in Inishowen, with their capital at Ailech; and the Cenél Conaill centered in the rich area of Magh Ithe, in the valley of the river Finn. For a time the Cenél Eóghain and Cenél Conaill alternated as kings of the Northern Uí Néill until the 8th century. The Northern Uí Néill would also alternate the High-Kingship of Ireland with their southern cousins the Southern Uí Néill into the 10th century.

The Cianachta, or the race of Kane, also known as Clann Cian, descend from Cian, son of Oilioll Ólum, king of Munster in the 3rd century. The territory of the Cianachta spanned the present-day barony of Keenaght, which derives its name from them. By the 12th century, the Cianachta would be conquered by the Ó Cathaín.

The Cianachta Glenn Geimin of Clann Cian, or the Cianachta of Glengiven, ruled a region now known as Dungiven.

The Síl Colla Fochríth, descend from Colla Fochríth, the first king of Airgíalla and one of Three Collas. Clans and septs that are claimed to descend from Colla Fochríth but with no other information given include; Ui Maine, Fir Dubhshlat, Ui Conaill, and Ui Luain.

Imchad was one of Colla Fochríth's sons, and from him son Muiredach Méth would descend the Uí Méith. The Uí Méith territory spanned northern County Louth, eastern County Armagh, and later in County Monaghan. John O'Donovan in his notes on the Annals of the Four Masters marks that there were two groups of the Ui Meith name; the Uí Méith Macha (or Uí Méith Tiri) and the Uí Méith Mara.

The Uí Méith Macha were based in the barony of Monaghan, County Monaghan. The Uí Méith Mara, meaning "Omeath by the sea", was seated in Cualigne in northern County Louth. The name Uí Méith survives as the present day name of the village Omeath.

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