Éogan Bél (d. 543), son of Cellach and overking of Connacht, probably belonged to the dynasty of Uí Fhiachrach. While an account in the Book of Leinster represents him as a son of the Uí Briúin dynast Duí Galach (alias Duí Tenga Uma?), the tradition that names his father as Cellach son of Ailill Molt (qv) of Uí Fhiachrach (Bk Uí Maine; AFM) seems more credible. Although the sixth century witnessed the consolidation of Christianity in Ireland, Éogan – like such contemporaries as Diarmait (qv) son of Cerball – is remembered for his alleged pagan associations. His sobriquet Bél suggests some connection with the Celtic god Belenus, whose festival of Beltene was held on 1 May. Éogan is credited with at least three sons including the founder of Killala Bishop Cellach (qv), Muiredach, and Ailill Inbanda. The late Irish Life of Cellach, which claims Éogan as the saint's father, also alleges, however, that Cellach and his brother Muiredach were slain by King Guaire Aidni (qv), who died in 663, which is completely anachronistic and discredits the source.
Éogan apparently became overking after the death of Duí Galach, which is assigned to the year 502. If he did not succeed Duí directly, Éogan attained the provincial dignity before too long; the king-list credits him with a reign of thirty-seven years. Historically, it seems that during Éogan's reign there was considerable conflict between the Connachta and the Uí Néill, who were not yet long established in their north-western realms. In 543 Éogan was defeated and slain in the battle of Slicech (Sligo) by an alliance that included Forggus and Domnall, sons of Muirchertach/Mac Ercae (qv), and Cenél Conaill dynasts Ainmire (qv) (d. 569) and Nainnid, sons of Sétnae. Another tradition, related in the Life of Cellach, maintained that Éogan was buried at Ráith Ua Fiachrach on Knocknarea, upright and facing his Uí Néill enemies till they had him disinterred and buried face downwards at Óenach Locha Gile.
Éogan's reputed son, Ailill Inbanda is named as his successor. He was in turn slain by the same Uí Néill alliance at Cúl Conaire (550). Later kings of Uí Fhiachrach are traced not to Éogan or to the line of Ailill Molt, but to parallel lineages.