Ó Muireadhaigh (O'Murry), Donatus (d. 1485), archbishop of Tuam, served as dean of Tuam before being provided by the pope to the see on 2 December 1450; he was consecrated sometime after December. Like many of his predecessors, he was faced with challenges to the union of Mayo and Annaghdown to his see, a dispute which dominated his time as archbishop. On his appointment to Tuam he had simultaneously secured appointment to Annaghdown. But though he was supported by the Burkes of Clanricard, Rome gave Ó Muireadaigh only equivocal support. Bishops were provided to both Mayo and Annaghdown by Rome even as the archbishop of Tuam's claims to these sees were being upheld. Mayo remained virtually independent till the 1470s, as Ó Muireadhaigh found when dealing with its bishops, Aodh Ó hUiginn (d. 1478), who was deprived sometime before January 1448, and his successor, Simon de Düren (d. 1470), an Augustinian.
Ó Muireadhaigh was more successful in his dealing with Annaghdown. Although Thomas Barrett (qv) was provided to the see in 1458, he was never able to gain any influence there, even with royal support. In 1460 it was reported that ‘Donatus, named archbishop of Tuam, born of the Irish race adverse to the king, destroys the lands of the said bishop [of Annaghdown] and of his men and tenants, and wages war against the bishop, who is born of the English nation’ (NHI, ii, 587). Ó Muireadhaigh forced out Barrett, who by 1465 was complaining that he had received nothing from his see for seven years (he became a suffragan bishop in Exeter and, later, Wells). In 1484 Ó Muireadhaigh devised a solution that ended the contention over the union of Annaghdown and Tuam. While he tightened his control over the rural areas of the diocese, he transferred ecclesiastical jurisdiction over Galway to the church of St Nicholas. By raising this church to the status of collegiate church and giving control of the elections to the citizens of Galway, he ended the decades-old quarrel over the union of the sees; he probably lived long enough to see his solution ratified by the pope.
The Annaghdown affair shows the animosity that existed in the church between the Gaelic Irish and the Anglo-Irish and also the ineffectiveness of the crown in the province of Tuam in the later fifteenth century. Indeed Ó Muireadhaigh was condemned by the crown in 1460 for refusing to ‘come to the king's parliaments and councils and to obey the laws of the land’ (ibid, 586).
Ó Muireadhaigh died 17 January 1485.