O'Corcoran, John (Ó Corcráin, Johannes) (d. 1389), Benedictine and bishop of Clogher; details of his birth and family are unknown, but it can be inferred that he was born in Ireland and most probably within the diocese of Clogher. At an unknown date, probably before the middle of the fourteenth century, he left Ireland and became a Benedictine at the Irish foundation in Würzburg, Franconia, known (like all Irish Benedictine foundations within the Holy Roman Empire) as the Schottenklöster. From there he was sent to study at the recently inaugurated University of Prague. Its founder, the Holy Roman Emperor Charles IV, had in a decree dated 11 December 1355 placed the convent in Würzburg under his special protection, and this may have inaugurated the link between the Irish monks and the new university. Unfortunately there are no surviving matriculation lists before 1372, so the precise date of O'Corcoran's arrival in Prague cannot be determined. There he acquired a degree in canon law, and in a petition to Pope Urban V on 6 February 1363 he is described as baccalaureus in decretis. He then received a benefice which was in the gift of the Cluniac abbey of Paisley, Renfrewshire, in the west of Scotland. In this document he is described not merely as a bachelor of canon law, but also as a candidate for the doctorate, who was already examinatus. It is unlikely that O'Corcoran ever resided in Scotland, and it is probable that he remained in Prague and subsequently (until his return to Ireland) in Würzburg, where on 26 November 1369 he headed the list of witnesses to a contract concerning the abbey's vineyards in the local Franconian wine region.
On 6 April 1373 Pope Gregory XI provided O'Corcoran to the episcopal see of Clogher, which seems to have been vacant since the death of Odo Ó Néill on 27 July 1369. The papal provision was made in response to election of the candidate by the cathedral chapter. O'Corcoran was clearly a member of the community inter Hibernicos, and appears to have been personally known to the chapter: he had obviously visited the diocese since his departure for the Continent. In Clogher O'Corcoran devoted himself with the assuidity of an experienced canon lawyer to the administration of his diocese, and presumably paid attention also to the most popular place of pilgrimage in Ireland, St Patrick's Purgatory in Lough Derg, which lay within his precinct. It is, however, noteworthy that no continental pilgrims who left record of their visit are to be found during the years of O'Corcoran's episcopate.
As bishop of Clogher he maintained close contact with his alma mater in Prague and returned there c.1380/81. This is all the more surprising in so far as Clogher lay at the end of the then known world, for the vast majority of Europeans. From here very few people undertook the long journey to the Continent, and when ecclesiastical dignitaries did so, they normally travelled to the papal court, either to Avignon or to Rome. At the university of Prague the degree of doctor decretorum, the doctorate in canon law, was conferred on him in a formal ceremony, during which a laudatio in honour of the bishop of Clogher was delivered. A brief summary of the text survives in two manuscripts. The text is based on a quotation from the book of Daniel (4, 7), ‘Ecce arbor in medio terre’, which has strong eschatological implications and which may be an allusion to O'Corcoran's connection with St Patrick's Purgatory, as the question of purgatory was at this time hotly debated in Prague. In view of the fact that O'Corcoran had already completed most of the requirements for the degree conferred on him, it was not simply a case of a doctorate honoris causa. However, his presence in Prague precisely during these years was probably linked with the discussion on purgatory.
A second possible reason for his return to Prague may have been in connection with the schism in the papacy, as the Bohemian capital was then the centre of intense diplomatic activity in this matter, and Clogher was a border diocese which, under another bishop, might have been inclined to revert to the Avignonese obedience.
It is not known how long O'Corcoran remained in Prague or whether he visited Würzburg on his return home. He died in Clogher c.1389 and his successor Art Mac Cathmhaoil was provided to the see on 15 February 1390.