Ailill Ollamh (orOilill Olum) in Irish traditional history was the son ofMug Nuadat and was a king of the southern half ofIreland, placed in the 3rd century by early modernIrish genealogy.Sadb ingen Chuinn, daughter ofConn of the Hundred Battles, in her second marriage, married Ailill. He divided the kingdom between his sonsÉogan Mór,Cormac Cas, and Cían. Éogan founded the dynasty of theEóganachta. Sadb's sonLugaid Mac Con, who was Ailill's foster-son, becameHigh King of Ireland.
TheBook of Leinster contains poems ascribed to him.
Several Irish surnames claim descent from Ailill Ollamh, reflecting a common tradition in Irish genealogy where families trace their lineage back to notable figures in mythology and history.An Leabhar Muimhneach (The Book of Munster) has an extensive genealogy of the Eóganacht septs.
In one of the oldest surviving tracts on the early history of theDeirgtine, the Proto-Eóganachta, Ailill is himself called adruid.[1] Furthermore, whether or not his father Mug Nuadat ever existed beyond some family association with the godNuada, Ailill is usually believed a relation or probable descendant ofNia Segamain.
