Conn Cétchathach (Conn of the Hundred Battles), legendary pre-Christian king of Tara, assigned to the 2nd cent. AD by later annalists and Gaelic historiographers. Ireland was divided between Conn and Eogan Mór of Munster into two political moieties demarcated by Escair Riada, a glacial esker extending east-west from Dublin to Clarinbridge, Co. Galway. Eogan, also known as Mug Nuadat (devotee of the god Nuadu), was killed at the Battle of Mag Léna in 177; but the southern half, called Leth Moga (Mog's Half) long remained under the control of his dynasty, the Eoganacht, centred at Cashel. The northern moiety, called Leth Cuinn (Conn's Half), was dominated in early medieval times by the Uí Néill, descendants of Niall Noígíallach (Niall of the Nine Hostages) and ultimately of Conn himself.

Conn Céadchathach
[Irish, of the Hundred Battles, the Hundred-Fighter].

Shadowy king of Irish pre-history and ancestor, perhaps ancestor-deity, of Irish kings. Although described in the annals as having lived in the 2nd century, Conn bears a name sometimes applied to rulers of the Otherworld. He is the first to hear from the Lia Fáil [the Stone of Prophecy], allowing him to foresee how many of his line will occupy the kingship as well as the coming of St Patrick. Along with his special role in kingship, he is also the eponymous ancestor of the Goidels of the midlands who named the province of Connacht (Connaught, Connachta, etc.) after him.

Conn's grandfather was the illustrious Tuathal Techtmar, but his father is variously named, most often Fedlimid Rechtaid (or Rechtmar) or Óenlám Gaba; his mother may be Medb Lethderg. The precocious Conn becomes king at Tara by seizing power from Cathaír Mór; by later interpolation he is aided by the Fianna of Fionn mac Cumhaill. Once in Tara, he mounts the ramparts each day lest the people of the sídh or the Fomorians should take Ireland unawares. In his early reign he is often at war with the petty kingdom of Dál nAraide to the east of Lough Neagh; here he earns his epithet of ‘Hundred Battles’ or ‘Hundred-Fighter’. His greatest rival is Eógan Mór (also Mug Nuadat) of Munster, with whom he divides Ireland. The division is made along a ridge of low mounds, known as Eiscir Riada, running from Dublin to Galway Bay. Territory north of that line is known as Leth Cuinn: Conn's half, and south of the line is Leth Moga Nuadat: Mug Nuadat's (Eógan's) half. Invading Munster, Conn defeats Eógan, who then flees the country; Conn instals two rulers, Conaire and Maicnia, more disposed towards him. Eógan returns, stirs up a revolt against Conn, and is defeated and slain at the Battle of Mag Léna (near Tullamore, Co. Offaly). Stories of Conn's own death differ. He may have been killed by thirty Ulstermen, led by Tiobraide Tíreach, dressed as women.

We read of Conn's adventures in some well-known texts. In Baile in Scáil [The Phantom's Frenzy], Conn learns of the future of his line from the Lia Fáil, and meets a beautiful woman who is the Sovereignty of Ireland. In Echtrae Airt meic Cuinn [The Adventure of Art Son of Conn], the fields of Ireland will bear no harvests and the cows will give no milk because Conn is mated with the disreputable Bé Chuma. Previously, when he was married to the virtuous Eithne Tháebfhota, daughter of Cathaír Mór, there were three harvests a year. When Conn's men kill Eochaid Bélbuide, he compensates Eochaid's protector, Fergus mac Léti, with a tract of land seized from the nobly born mother of one of the assassins, Dorn, who becomes Fergus's slave.

Conn is often mentioned in the Fenian Cycle, although the stories there appear to be of later composition. Fionn mac Cumhaill is usually thought to have been born during the reign of Conn or that of his predecessor, Cathaír Mór. In some versions, Conn killed Cumhall, Fionn's father, for his abduction of Muirenn, Fionn's mother. Despite this, Fionn and his Fianna are often seen as Conn's allies. Among Conn's children are the aforementioned Art mac Cuinn as well as Connla, who is seduced by a fairy princess in Echtrae Conli [The Adventure of Connla]. A daughter is Sárait, mother of three Cairbres. His grandson is the celebrated king Cormac mac Airt. His druid was Máel or Corán. In Gaelic Scotland the Lord of the Isles of the Clan Donald proudly claimed descent from Conn as well as from Colla Uais.