Ó Cuív, Brian (1916–99), Irish-language scholar, was born 20 November 1916 in Dublin, sixth child of Shan Ó Cuív (qv), journalist, and his wife Hannah O'Keeffe. He was educated at the O'Connell Schools and afterwards matriculated to UCD in 1935. During his time as a student he was elected secretary of the Irish Society in the College and was a representative on the Oireachtas na Gaeilge committee. He graduated with a BA in Celtic studies in 1938 and two years later with an MA in Irish. He was then appointed lecturer in early and medieval Irish and Welsh in St Patrick's College, Maynooth, and remained there until 1942, when he transferred to the School of Celtic Studies in the DIAS as a research assistant. Two years later he was appointed assistant professor, and in 1951 he was appointed professor. He moved to UCD in 1953 to take up the post of lecturer in classical Irish language and literature, and subsequently became professor of Classical Irish language and literature there (1960–67). In 1967 he returned to the School of Celtic Studies as senior professor, and in 1968 was appointed director of the school, a post he held until 1973. He was elected MRIA (1951) and awarded a D.Litt. by the NUI (1955).
Ó Cuív was one of the foremost Irish-language scholars of the twentieth century and shared his knowledge generously with the next generation. An expert on Classical Irish, he also published widely on other aspects of the language such as dialects, grammar, metrics, literature, and history. Over 300 of his publications are listed by Rolf Baumgarten in Bibliography of Irish linguistics and literature 1942–71 (1986), but a complete list is lacking. His writings include The Irish of West Muskerry, Co. Cork (1944); Cath Muighe Tuireadh (1945); Cnósach Focal ó Bhaile Bhúirne i gcunndae Chorcaí (1947); Irish dialects and Irish-speaking districts (1951); Párliament na mban (1952); ‘Literary creation and Irish historical tradition’, Proceedings of the British Academy, xlix (1965); ‘The linguistic training of the mediaeval Irish poet’, Celtica, x (1973); The Irish bardic duanaire or ‘poem book’ (1974); his contributions to volumes iii (1976), iv (1986) and vi (1996) of A new history of Ireland; Aspects of Irish personal names (1986); Aisling Meic Conglinne (1990), a work begun by Kenneth Jackson (qv) before his health failed; and Aibidil Gaoidheilge agus caiticiosma: Seaán Ó Cearnaigh's Irish primer of religion published in 1571 (1994). He was editor of two series of Thomas Davis lectures broadcast on Radio Éireann, resulting in the publications Seven centuries of Irish learning 1000–1700 (1961) and A view of the Irish language (1969). He was editor of the journals Éigse and Celtica, of which vol. xxi (1990) was published as a Festschrift in his honour. He died in Dublin 14 November 1999 and is buried in Glasnevin cemetery. His final publication, Catalogue of Irish language manuscripts in the Bodleian library at Oxford and Oxford college libraries, appeared posthumously (2001–3).
He married (15 April 1941) Emer, daughter of Éamon de Valera (qv); they had four daughters and five sons, their sixth child and second son being Éamon Ó Cuív, Fianna Fáil TD and government minister.