Ailill Finn, son of Art mac Lugdach

Art mac Lugdach

Art, son of Lugaid Lámderg, was, according to medieval Irish legend and historical tradition, a High King of Ireland. He took power after killing his predecessor, and his father's killer, Conaing Bececlach. He ruled for six years, until he was killed by Fíachu Tolgrach and his son Dui Ladrach...

, was, according to medieval Irish legend and historical tradition, a High King of Ireland

High King of Ireland

The High Kings of Ireland were sometimes historical and sometimes legendary figures who had, or who are claimed to have had, lordship over the whole of Ireland. Medieval and early modern Irish literature portrays an almost unbroken sequence of High Kings, ruling from Tara over a hierarchy of...

. In the Lebor Gabála Érenn

Lebor Gabála Érenn

Lebor Gabála Érenn is the Middle Irish title of a loose collection of poems and prose narratives recounting the mythical origins and history of the Irish from the creation of the world down to the Middle Ages...

, he succeeds to the throne when his father is killed by Fíachu Tolgrach and his son Dui Ladrach. He rules for nine years. Two years into his reign, Fíachu Tolgrach is killed in battle against Airgetmar, son of Sírlám

Sirlám

Sírlám, son of Finn mac Blatha, was, according to medieval Irish legend and historical tradition, a High King of Ireland. He took power after killing his predecessor, Lugaid Íardonn, in Ráth Clochair. His name means "long hand" or "long arm", and it is said his arms reached the ground when was...

. The men of Munster

Munster

Munster is one of the Provinces of Ireland situated in the south of Ireland. In Ancient Ireland, it was one of the fifths ruled by a "king of over-kings" . Following the Norman invasion of Ireland, the ancient kingdoms were shired into a number of counties for administrative and judicial purposes...

, led by Ailill's son Eochu and Lugaid, son of Eochu Fíadmuine, then drive Airgetmar into exile overseas. After seven years Airgetmar returns to Ireland and kills Ailill with the help of Dui Ladrach and his son Fíachu, but is unable to seize the throne, which is taken by Eochu.

However, in Geoffrey Keating

Geoffrey Keating

Seathrún Céitinn, known in English as Geoffrey Keating, was a 17th century Irish Roman Catholic priest, poet and historian. He was born in County Tipperary c. 1569, and died c. 1644...

's Foras Feasa ar Éirinn and the Annals of the Four Masters

Annals of the Four Masters

The Annals of the Kingdom of Ireland or the Annals of the Four Masters are a chronicle of medieval Irish history...

Fíachu Tolgrach succeeds to the throne after killing Art, and is later killed by Ailill, who then takes the throne, and rules for nine or eleven years, before being killed by Airgetmar and succeeded by Eochu.

The Lebor Gabála synchronises his reign with that of Artaxerxes II of Persia

Artaxerxes II of Persia

Artaxerxes II Mnemon was king of Persia from 404 BC until his death. He was a son of Darius II of Persia and Parysatis.-Reign:...

 (404-358). The chronology of Keating's Foras Feasa ar Éirinn dates his reign to 586-577 BC, that of the Annals of the Four Masters to 795-786 BC.

He is given as an ancestor of the Gamarad of Nephin

Nephin

Nephin or Nefin , at 806 metres , is the second highest peak in County Mayo and the second highest in Connacht, in Ireland...

, County Mayo

County Mayo

County Mayo is a county in Ireland. It is located in the West Region and is also part of the province of Connacht. It is named after the village of Mayo, which is now generally known as Mayo Abbey. Mayo County Council is the local authority for the county. The population of the county is 130,552...

.