Born in New Zealand to Irish parents, O’Farrell moved to Australia in 1956 and, after receiving a PhD from the Australian National University, became a professor of history and, later, emeritus professor, at the University of New South Wales (UNSW).
Many of the 12 books he wrote concerned Irish Australia, Catholicism in Australia and Anglo-Irish relations. His most famous work, The Irish in Australia, first published in 1987, remains the most thorough account of the shared history of the two countries. As he said himself: “If people don’t know history, they don’t know themselves.”
At the time of O’Farrell’s death on Christmas Day 2003, UNSW Vice-Chancellor, Prof Rory Hume, said he had made “landmark contributions to the study of Irish-Australian history and Australian Catholicism”.
Then Irish ambassador to Australia Declan Kelly said: “The government and the people of Ireland owe him an enormous debt of gratitude for his scholarly work.”
O’Farrell held visiting professorships at both Trinity College (1965-66) and University College Dublin (1972-73).
He is survived by his wife Deirdre and their five children.