Saint Nath Í, or Crumnathy, (fl. 6th century) was an early Irish saint who was remembered as the founder of Achonry. He is said to have been born in the barony of Leyney, in present-day Co. Sligo. In the 17th century, John Colgan compiled a Latin Life of St Cormac, published in the Acta Sanctorum Hiberniae series, which relates that Cormac left his native Munster for Connacht and arrived in the area of Leyney. When Niall, the brother of the local chieftain Diarmait, begged the saint for a blessing, Cormac revealed that he was to have a son by the name of Conamel, whose descendants would include a number of illustrious saints, such as Náth Í "the priest". In the Martyrology of Donegal (9 August), he is described as the priest (cruimthir) Nath Í of Achad Cain Conairi.