Séamus mac Pilib Mac Mathghamhna
|Séamus mac Pilib Mac Mathghamhna|
|Bishop of Derry|
|Church||Roman Catholic Church|
|Predecessor||Domhnall Ó Fallamhain
|Successor||Ruaidhrí Ó Domhnaill
|Born||Clones, County Monaghan|
Séamus mac Pilib Mac Mathghamhna (died 1519) was the Bishop of Derry.
He was appointed Bishop-designate of Clogher on the 5 November 1494. John Edmund de Courcy was also Bishop of Clogher around this time and he did not renounce his claim to Clogher until 1502. Séamus then became Bishop of Derry from 26 November 1503 up until his death in 1519.
He was the son of the Coarb of Clones Abbey, Pilib mac Séamus Mac Mathghamhna  and great-grandson of, Ruaidhri mac Ardghail Mor Mac Mathghamhna, who was King of Oriel from 1442–1446. His uncle, Niall mac Séamus Mac Mathghamhna (died 1488), was also appointed Bishop of Clogher before 14 June 1484, but the papal bulls were not expedited, John Edmund de Courcy went on to become Bishop instead. The Annals of the Four Masters mention his brother Niall who died on his way from Rome in 1484.
- Fryde, E. B.; Greenway, D. E.; Porter, S.; Roy, I. (1986). Handbook of British Chronology (Third Edition). Cambridge: Cambridge University Press. pp. 337–339. ISBN 0-521-56350-X.
- Cotton, Henry (1849). The Succession of the Prelates and Members of the Cathedral Bodies of Ireland. Fasti ecclesiae Hiberniae. Vol. 3, The Province of Ulster. Dublin: Hodges and Smith. p. 314.
- Fryde, ibid., p. 346.
- translation/ Annals of Ulster 1486 page 303 note:Art, son of Mac Domnaill of Clann-Cellaigh, namely, son of Cormac, son of Art Mac Domnaill, was slain in Cluain-eois, in a quarrel he made with clerics Little Christmas Day (namely, with Seamus mac Pilib, son of the Coarb Mag Mathgamna and with the son of Donchadh Mag Mathgamna, that is, the Parson and with Gilla-Padraig O'Connalaigh, that is, the Abbot)
-  Annals of the Four Masters note: Rudhraighe mac Ardghail Moir Mheg Mathgamhna tighearna Oirghiall do écc. & a mhac Aedh Ruadh mac Rudhraighe do oirdneadh ina ionad la h-Ua Néill.
- edition, translation Vol. 5 (AD 1501–1588): p.1342 Note:(M1519.1 Semus mac Pilib mic Semais mic Rudhraighe Még Mhathgamhna epscop Doire d'écc.)
-  Annals of the Four Masters Part 12 note: M1484.3 Niall, son of the Coarb Mac Mahon, died on his way from Rome