Thomas Francis O'Rahilly, also Tomás Ó Rahille, born 1883 in Listowel, County Kerry, Ireland; died 1953 in Dublin, was an influential scholar of the Celtic languages, particularly in the fields of Historical linguistics and Irish dialects. He was a member of the Royal Irish Academy.

Educated at the Royal University of Ireland , he held professorships in Irish at Trinity College, Dublin (1919-1929), and in Celtic languages at University College Cork (1929-1935) and University College Dublin (1935-1941). He was director of the School of Celtic Studies at the Dublin Institute for Advanced Studies from 1942 to 1947.

O'Rahilly was known for his sometimes controversial theories of Irish history. In his book Early Irish history and mythology, first published in 1946, O'Rahilly developed a model of Irish prehistory based on critical reading of early Irish literary sources, involving four waves of Celtic-speaking invaders (see Early history of Ireland). In a lecture publiched in 1942 he proposed that there were two Patricks.

His views on language contact and bilingualism were equally controversial. In Irish dialects past and present (1932) he wrote the following about Manx:

From the beginning of its career as a written language English influence played havoc with its syntax, and it could be said without much exaggeration that some of the Manx that has been printed is merely English disguised in a Manx vocabulary. Manx hardly deserved to lived. When a language surrenders itself to foreign idiom, and when all its speakers become bilingual, the penalty is death. (p. 121)

Other publications include and a series of anthologies of Irish verse published between 1916 and 1927. He founded and edited Gadelica: a Journal of Modern Irish studies, and edited the journal Celtica (1946-1950).

External links

• T. F. O'Rahilly Papers
• Thomas Francis O'Rahilly - a family history page
• T. F. O'Rahilly