Muiris mac Donnchadh Ulltach Ó Duinnshléibhe

Muiris mac Donnchadh Ulltach Ó Duinnshléibhe (fl. 1602-1630s), anglicised Maurice MacDonough Ultach Donlevy, also known as Muiris Ulltach, was an Irish Franciscan cleric. He was born into the Ó Duinnshléibhe family, a hereditary medical family of physicians to the O'Donnells, based in County Donegal. Some members of the family went by the surname Ultach, named after the over-kingdom Ulaid, of which they were formerly the ruling dynasty.

The Annals of the Four Masters describe him as "a poor friar of the order of St. Francis" from the convent of Donegal's monastery. In September 1602, Ó Duinnshléibhe attended clan chief Hugh Roe O'Donnell on his death bed in Simancas Castle, Spain. Also attending were O'Donnell's spiritual adviser, Fláithrí Ó Maolchonaire (future Archbishop of Tuam)

Contributions to Annals In the 1630s, both Ó Duinnshléibhe and Muiris mac Seaán Ulltach Ó Duinnshléibhe were attached to the Franciscan convent at Bundrowes, and became acquainted with chronicler Mícheál Ó Cléirigh, who was then compiling the Annals of the Four Masters. Ó Duinnshléibhe's recollections of events, including the death of O'Donnell, were incorporated into the compilation.