Donough O’Brien was born on 24 June 1911 in Dublin, Ireland. He was brought up on the family’s country estate in County Limerick and later won scholarships to Bromsgrove School in England and to Trinity College Dublin, where he began a medical course in 1929. He graduated top of his year, with first class honours, in 1934. In 1939, he gained Fellowship of the Royal College of Surgeons (Ireland) and was awarded the Surgical Travelling Prize.