Ailill Ólom, mythical Munster king and ancestor figure of the free lineages of Munster, appears in alternative genealogical traditions either as son of Éogan Már (qv), ancestor of the Éoganacht dynasties, or as son of Mug Núadat and father of Éogan Már. The saga ‘Cath Maige Mucrama’ has Ailill abdicate the kingship of Munster in favour of Éogan. The same tale maintains that he ravished Áine, daughter of Éogabul (‘yew-fork’), at Cnoc Áine in Limerick. She chewed the flesh off his ear; hence the sobriquet Ólom or Aulomm (bare-eared). He is also alleged to have married Sadb, daughter of Conn Cétchathach (qv), who bore him seven or nine sons. In total, the genealogists credit him with nineteen sons, many of whom are clearly duplications.
The historical significance of Ailill lies in the number of dynasties that claimed descent from him. Aside from his being an ancestor of Éoganacht Chaisil, his alleged sons Cormac Cas and Cian founded the dynasties of Dál Cais (later very prominent in Irish history) and of the Cianachta, Gailenga, and Luigne. He is also claimed as an ancestor of the ruling lineages of Delbna Bethra and Cerddraige.