Dillon, Myles Patrick (1900–72), Celtic and Sanskrit scholar, was born 11 April 1900 in Dublin, third son among five sons and one daughter of the Irish nationalist leader John Dillon (qv) and his wife Elizabeth, eldest daughter of the Rt Hon. Sir James Charles Mathew (qv), PC. He was educated in Belvedere College, Dublin, and Mount St Benedict in Gorey, Co. Wexford, entering UCD in 1917, where he studied classical languages before switching to Celtic studies. There he studied under Osborn Bergin (qv) who introduced him to Sanskrit. He received his BA and MA degrees in 1921 and 1922, both with first-class honours.
From 1922 to 1927 a travelling studentship in Celtic studies from the NUI brought him to Berlin, Bonn, Heidelberg, and Paris, studying comparative philology, with an emphasis on Sanskrit and Celtic languages. He received his doctorate from Bonn University in 1925, having been supervised by Rudolf Thurneysen (qv). The correspondence of Myles Dillon, 1922–1925: Irish-German relations and Celtic studies (1999) comprises letters he exchanged, mostly with his father, during his sojourn in Germany. In 1928 he was appointed lecturer in Sanskrit and comparative philology in TCD. Two years later he accepted a similar position in UCD, where he remained until 1937. It is believed that his failure to succeed Douglas Hyde (qv) to the chair of Irish in 1932 was a result of his opposition to compulsory Irish in the education system. It was also probably owing in part to his unpopular view that home rule would have been better for Ireland than the settlement that emerged after the Anglo–Irish war. He left Ireland in 1937 to take up the newly created position of chair of Irish in the University of Wisconsin, where he remained until 1946, when he was appointed professor of Celtic philology and comparative linguistics in the University of Chicago. The following year he was appointed professor of Celtic in the University of Edinburgh. On his return to Ireland in 1949 he was appointed senior professor in the School of Celtic Studies in the Dublin Institute for Advanced Studies, where he later served as director (1960–68).
As a lecturer he was much in demand internationally and frequently travelled abroad, visiting centres of learning in Europe, Asia, America, and Australia. In 1969 he received a two-year fellowship from the Indian Institute of Advanced Study, which took him to India as visiting research professor. This resulted in the posthumous Celts and Aryans: survivals of Indo-European speech and society (1975). Among the many honours he received during his career were the vice-presidency of the Linguistic Society of America (1947), the presidency of the Irish Texts Society (1959–72), and honorary degrees from the universities of Wales, Rennes, Louvain, Oslo, Belfast, and Edinburgh. A member of the RIA since 1929, he was elected president in March 1966 but resigned the following December.
He was author, co-author, or editor of more than 200 publications on Celtic studies and Sanskrit, including The cycles of the kings (1946), The archaism of Irish tradition (1948), Early Irish literature (1948), Early Irish society (1954), Irish sagas (1959), Teach yourself Irish (1961), and The Celtic realms (1967). He also served as editor of the journal Celtica for many years. After a short illness, he died 18 June 1972 in Monkstown hospital, Co. Dublin, and was buried in Glasnevin cemetery.
He married (24 August 1938) Elizabeth Mary La Touche, youngest daughter of naturalist John (Jean) David Digues La Touche and Caroline Focken. The Dillons lived at Drumnigh House in Portmarnock, Co. Dublin. Myles had sold his family home at 2 North Great George's St. in the early 1940s. They had two daughters and three sons, including John Myles Dillon, sometime professor of Greek at TCD, and Robert Peter (Fr Christopher, OSB), sometime abbot of Glenstal.