Airgeatmhar, son of Sirlám, was a legendary High King of Ireland. The office of High King of Ireland (Irish: Ard Rí Érenn) was in origin a pseudohistorial construct of the eighth century that placed a king of all Ireland atop the fragmented pyramid of kingship that actually existed at that time. ...

He and Duach Ladhgrach killed Ailill Finn, who was then High King, but Ailill's son Eochaid was able to withstand them and keep the kingship. But when Eochaid held a meeting with Duach to discuss peace, Duach betrayed and murdered him, and Airgeatmhar took the kingship. Eventually he was himself overthrown by Duach. Ailill or Oilioll Finn, son of Art mac Lugdach, was a legendary High King of Ireland. ...

The High Kingship of Ireland was a pseudohistorical construct of the eighth century AD, a projection into the distant past of a political entity that did not become reality until the ninth century. ... Signature page from the Annals of the Four Masters Entry for A.D. 432 The Annals of the Four Masters or the Annals of the Kingdom of Ireland by the Four Masters are a chronicle of medieval Irish history. ... Seathrún Céitinn, known in English as Geoffrey Keating, was a 17th century Irish clergyman, poet and historian. ...