In Irish traditional history Eógan (or Eoghan Mór—a name also used by his grandfather, Mug Nuadat), eldest son of Ailill Ollamh, was a 2nd or 3rd century AD king of Munster.
[4] He was the father of Fiacha Muillethan, and in order to conceive his son, he slept with Moncha, the daughter of Dil the night before Maige Mucrama so that he would have an heir before he died.
The modern irish clans that trace their genealogy back to Éogan Mór are the Clancarthy Mores, the Mac Carthys, the O Sullivans, O Ciarmhaics and the O Bryens.
[1] Éogan Mór is also featured in the Cath Maige Mucrama, an early middle Irish tale which forms part of the cycle of the kings[7] This story is found in the book of Leister which is dated to the 12th century.
As the two brothers awake, they nonetheless still demand that Ailill Aulom lay down a judgment, to which he remarks “small advantage” (bec torbai).
The credit for defeating Mac Conn is claimed by three people- Éogan Mór, Cairpre Musc, and this Gnathal,ancestor of the Muscraighe Mittene.