Mac Cana, Proinsias (1926–2004), Celtic scholar, was born 6 July 1926 in Belfast, son of George McCann and his wife Mary Catherine (née Mallon). He grew up in a catholic district in east Belfast, where inter-community tensions were keenly felt. He attended St Malachy's College during the war years (1939–44), and began his academic studies at Queen's University, Belfast, in 1944. His interest in the Irish language was slow to blossom, either at school or at university, where he originally intended to focus on English studies, only to be discouraged by an uninspiring teacher. Having switched to Celtic studies, then without a head of department, he was awarded a first class honours degree in 1948 and, assisted by a studentship from QUB, he continued his studies at the École des Hautes Études (1948–9) under the noted French scholar, Joseph Vendryés (1875–1960), while also attending lectures by the mythologist, Georges Dumézil. This led to a lifelong engagement with French scholarship on the Celtic languages, marked by several important articles published in the Celtic journal Études Celtiques. These included two of his most influential essays: 'Aspects of the theme of king and goddess in Irish literature' (Études Celtiques, vii (1955–6), 76–114; viii (1958–9), 59–65) and 'Conservation and innovation in early Celtic literature' (ibid., xiii (1972–3), 61–119). His time in Paris also led to a lasting interest in the fortunes of the Irish colleges in France, made evident by his Collège des Irlandais: Paris and Irish studies, which was published in Dublin in 2001.
Returning to Ireland in 1949, he graduated MA in 1950 and went on to prepare a Ph.D. thesis on 'Early Irish literature' (presented and awarded in 1953), while employed as an assistant lecturer (1951–4) and temporary lecturer (1954–5) in the Celtic department at QUB. On 3 September 1952 he married Réiltín (Stella) Supple; they had one son and one daughter. He published his first papers, under the still anglicised form of his name (Frank McCann ), in the Bulletin of the Ulster Place-Name Society (vols i, ii). Appointed assistant lecturer in Old and Middle Irish in the University College of Wales, Aberystwyth, in 1955, and lecturer (1957–61), he embraced wholeheartedly the opportunity this presented of extending and deepening his knowledge of Welsh language and literature. Not only did he become the epitome of Irish scholarship for his Welsh colleagues, he attained a lasting respect as a media commentator in fluent Welsh on wider Irish political and social affairs. Within three years of his arrival in Aberystwyth, he published an authoritative and oft-cited monograph on Branwen daughter of Llyr: a study of the Irish affinities and of the composition of the second branch of the Mabinogi (Cardiff, 1958), and he later returned to this subject in The Mabinogi, published by the University of Wales Press in 1977 (reprinted 1992). His first book, which he edited with Tomás Ó Floinn, was Scéalaíocht na ríthe ('Stories of the kings') (1956); it was illustrated by Micheál MacLiammóir (qv), and reissued in 2010.
Shortly after his return to Ireland in 1961 to take up a professorship in the Dublin Institute for Advanced Studies (DIAS), he became the obvious choice of successor to John Lloyd Jones (d. 1956) in the chair of Welsh at UCD. Appointed in 1963, he held the chair until 1971, when he was elected to the position of professor of early (including medieval) Irish language and literature at UCD, as successor to Francis Shaw (d. 1970). Shortly before this, he published Celtic mythology (London, 1968; revised 1983), a book which remains one of the standard works on the subject. He often jokingly remarked that, had he known how successful the book would be, he would have insisted on a much more favourable contract with the publishers. His time at UCD, which lasted until 1985, saw him become a member of the Royal Irish Academy (1970–2004), of which he held the presidency between 1979 and 1982. He chaired with tact and shrewdness the editorial committee of the RIA's Dictionary of Irish Biography project until his death in 2004, and was a constant source of support and encouragement to the managing editor. He chaired too the editorial committee of the RIA's Dictionary of Medieval Latin from Celtic Sources project. He was also appointed chairman of the governing board of the School of Celtic Studies at the DIAS in 1975, retaining this position for ten years. By way of marking his continuing interest in placenames, he was appointed to the Irish Placenames Commission in 1975, remaining a member until 2003. In 1978, he published in the Crane Bag 'Notes on the early Irish concept of unity'.
Resigning from UCD in 1985, he was appointed senior professor at the DIAS, a position he retained (as emeritus from 1996) until his death in 2004. Between 1987 and 1992, while in DIAS, he availed himself of the opportunity to take up the offer of a professorship of Celtic languages and literatures at Harvard during each fall semester. A measure of his lasting influence on American Celtic scholars is the fact that two of the editors of the Festschrift presented to him in 1999 were Harvard graduates (J. Carey, J. T. Koch, and P.-Y. Lambert, ed., Ildánach Ildírech: a Festschrift for Proinsias Mac Cana (Andover and Aberystwyth, 1999)).
Although also active in other spheres, including his involvement in the civil rights movement for Irish speakers in Donegal, it is as a scholar that Mac Cana will be best remembered. While the main focus of his research was on early Irish literature, an area in which many of his published articles and books remain highly influential, he also continued to publish widely on aspects of Welsh language and literature throughout his career. His last substantial essay on 'Praise poetry in Ireland before the Normans' (Ériu, liv (2004), 11–40) contains several pages (36–40) on 'The testimony of Welsh'. He was awarded three honorary degrees, at the universities of Dublin (1985), Ulster (1991) and Wales (1995). As co-editor of Ériu for over thirty years (1973–2004), he contributed greatly to the scholarly journal's success and high standing. It was his painful duty during these years to write obituaries of two fellow editors and friends, David Greene (qv) (Ériu, xxxiv (1983), 1–10) and Gordon Quin (Ériu, xxxviii (1987) 1–3). In his own final contribution, published as an introduction to the 2004 centenary volume, he stressed the privilege and pleasure that the editorship had given him, before going on to announce his decision to retire in favour of a younger scholar (Ériu, liv (2004), 1–2). His sudden death on 21 May 2004 at his home in Glenageary, Co. Dublin, deprived Celtic scholars, young and old, of an inspirational mentor and colleague.