Bishop O’Reilly was born on 8 August 1952. Following university studies in St. Patrick’s College (Maynooth), he was ordained to the priesthood on 17 June 1978 in the African Missions Church at Wilton, Cork. He was then appointed to pastoral work in the Archdiocese of Monrovia (Liberia).
Two years later, Mgr. O’Reilly was recalled to undertake studies in Sacred Scripture at the Pontifical Biblical Institute in Rome, from where he qualified with a licentiate in Sacred Scripture. His next appointment was to the Major Seminary of SS. Peter and Paul, Ibadan (Nigeria) where he lectured in Sacred Scripture for five years.
Six years later, at the 1995 SMA General Assembly in Rome, Archbishop Kieran was elected the SMA Vicar General. As a member of the General Council, he was responsible for several matters – formation of seminarians and priests; justice and peace issues and the development of the SMA in Africa. In 2001 he was elected the eleventh Superior General of the Society of African Missions a position he held until 2010 when he was appointed Bishop of Killaloe.
Mgr. O’Reilly is Delegate of the Irish Bishops’ Conference to COMECE since March 2023.