O'Kelly, Michael Joseph (‘Brian’) (1915–82), archaeologist, was born 5 November 1915 in Springmount, Abbeyfeale, Co. Limerick, son of Joseph O'Kelly, a national school teacher, and Elizabeth O'Kelly (née McAuliffe). After receiving secondary education at Rockwell college, Co. Tipperary, he entered UCC in 1934 to study engineering. Switching interests after the first year to architecture, he was articled to the office of Henry Hill in Cork, where he gained valuable training in surveying and architectural drawing, but never qualified as an architect. Engaged by Professor Seán P. Ó Ríordáin (qv) in spring 1937 as surveyor on an archaeological dig at a ring-fort at Garranes, Co. Cork, he was inspired to switch interests again, and in autumn 1937 entered UCC's department of archaeology, where he studied under Ó Ríordáin. He gained field experience by working on the important excavations at Lough Gur, Co. Limerick, where he soon became Ó Ríordáin's chief assistant. Taking a first class honours BA in 1940, he was awarded an MA in archaeology with first class honours in 1941 for a survey of the antiquities of the barony of Small County, Co. Limerick, for which he also won the NUI's travelling studentship in archaeology. Prohibited by wartime restrictions from researching on the continent or in Britain, he undertook an intensive study of the souterrain in Ireland, but abandoned his aspiration to compose a doctoral thesis on the subject owing to the scholarly necessity of supplementing his findings with field work in France and Germany. In 1942 he joined the staff of the Topographical and Archaeological Survey conducted by the Irish Tourist Association; becoming director of the survey the following year, he was responsible for preparing a new series of tourist guides. As the first curator of the newly founded Cork Public Museum (1944–63), he set up the collection for the formal opening in April 1945, and over time established the institution's status as a major local centre of education, research, and culture. In 1945 he undertook his first major solo excavation, of two ring-forts at Garryduff, Clonmult, Co. Cork, where he made the celebrated discovery of the Garryduff gold bird. Succeeding Ó Ríordáin as professor of archaeology at UCC, he occupied the chair for thirty-six years (1946–82), expanding the department's size and scope, and moulding it into one of the leading university departments in the discipline; he also continued as part-time curator of the Cork museum till its administrative link with UCC was severed in 1963.
O'Kelly's research embraced a remarkably wide range of archaeological enquiry. A keen student of ancient technologies, he published revolutionary re-interpretations of the manufacturing methods employed by the makers of several well-known metal objects, notably the Iron Age triad of the Cork horns, the Petrie crown, and the Bann disc, and the early-Christian Moylough belt shrine. He conducted experiments, which included gastronomic tests, investigating the operational methods of the ancient cooking places known as fulachta fiadh; he also experimented to determine the ancient method of smelting iron. His dozen major excavations included megalithic tombs, ecclesiastical sites, and domestic settlements, from the neolithic period to the medieval. He is best known for conducting, over fourteen seasons (1962–75), the first systematic excavations, combined with conservation and restoration, of the megalithic passage tomb and ancillary monuments at the famous site of Newgrange, Co. Meath. Most dramatic of his discoveries there was the roof-box over the passage entrance, a feature unique in the megalithic architecture of western Europe, situated so as to allow the light of the rising sun at the winter solstice to pass through a narrow gap in the stones and penetrate the full length of the passage and illuminate the chamber. He conducted the first reliable Carbon 14 dating for the construction of the cairn, set at 3200 BC, thus establishing Newgrange as the oldest known celestially aligned structure in the world. On the basis of an engineer's analysis of the cairn collapse, he oversaw the erection of a three-metre-high, subvertical revetment wall at the south front of the cairn composed of white quartz stones and randomly placed granite boulders found during the excavations, thus restoring the monument to what he hypothesised was its original appearance. A controversial feature, the wall – likened by one observer to a cheese-cake with dried currants – has been contextualised by some later scholars as representative of 1960s fashions in restoration; a few have urged its removal. O'Kelly's definitive report on the excavations, Newgrange: archaeology, art, and legend (1982), was published several weeks after his death.
With his original and creative mind, indifference to accepted wisdom, zeal to test hypothesis with experiment, and breadth and depth of interests, O'Kelly exerted a profound influence on the development of archaeology in Ireland. Remarkable for the swift and thorough publication of his research findings, he contributed some seventy-five articles to scholarly journals, and wrote numerous reviews, and articles in popular periodicals. On the basis of twenty of his published papers, comprising regional surveys, excavation reports, theoretical analyses, and technological studies, he was awarded a D.Litt. by the NUI (1963). A member of the Cork Historical and Archaeological Society from 1942, he served twice as president, and was for many years editor of the society's journal (1947–64). He was a long-serving and influential member of the National Monuments Advisory Council, which he chaired from 1966 to 1970, and a long-time member and a vice-president (1977–82) of the North Munster Antiquarian Society. A fellow from 1947 of the Society of Antiquaries of London, in 1948 he was elected a member of the RIA, and served for many years on the academy's national committee for archaeology. He was a state nominee on the statutory board of visitors of the National Museum of Ireland, a vice-president of both the RSAI and the Prehistoric Society, and a member of the permanent council of the International Union for Prehistoric and Protohistoric Sciences.
He married (1945) Helen Claire O'Donovan, a national teacher, whom he had met as a fellow archaeology student in UCC; they had three daughters, and resided at Ardnalee, Blackrock, Cork. Claire O'Kelly assisted her husband in numerous aspects of his archaeological research, and made a study of the monumental art of Newgrange and the other Boyne valley tombs, published in Proceedings of the Prehistoric Society (1973) and summarised in her Illustrated guide to Newgrange and the other Boyne monuments (1978). The couple collaborated on an Illustrated guide to Lough Gur (1978). Brian O'Kelly died suddenly in the Bon Secours hospital, Cork, on 14 October 1982, and was buried in St Michael's cemetery, Blackrock. Before his death he had completed a draft of a general introductory synthesis of Irish prehistory, which was edited and updated by Claire O'Kelly and published as Early Ireland (1989). A Festschrift, Irish antiquity (1981), edited by Donnchadh Ó Corráin, includes a biographical introduction by E. Estyn Evans, and a comprehensive bibliography of O'Kelly's publications.