A leader of the Milesians in the pseudo-history Lebor Gabála [Book of Invasions], the first of his people to reach Ireland. Son of Breogan in Spain, he sails to Ireland to settle a dispute among the Tuatha Dé Danann, but his eloquence makes the disputants fear that he seeks to be king and so they kill him. His nephew, Míl Espáine, avenges his murder with the invasion of Ireland. His name is commemorated in several places on the Irish map, e.g. Mag Ítha, Co. Donegal. Imaginative medieval genealogists placed his name in many pedigrees. The fictitious king Eochaid mac Luchta traced his line to Íth. The mythic hero of the Érainn, Lugaid mac Con, was given Goidelic heritage by inventing the patronymic and identity of Lugaid mac Ítha. Often confused with Ír.