John Kirby was born in Baylough, Athlone, the son of Patrick Kirby and Rose McCormack. After his primary education in ‘The Batteries’ National School, Athlone and secondary education in St. Joseph’s College, Garbally Park, Ballinasloe, he went to St. Patrick’s College, Maynooth to study for the priesthood.
He was ordained on Sunday, June 23rd, 1963 and his first appointment as a priest was as teacher in St. Joseph’s College, Garbally. His main subject was mathematics, which he taught to honours leaving certificate level. During his years in Garbally he involved himself in every aspect of college life and had considerable success as trainer of the senior Rugby Football team. In September 1979, when Fr. Joseph Cassidy was appointed Coadjutor Bishop of Clonfert, he was appointed President and Principal of Garbally College. The college was entering a period of rapid growth at that time and Fr. Kirby oversaw a major building project to extend the classroom accommodation and facilities for staff and students.
In 1988 Bishop Cassidy was transferred to the diocese of Tuam as archbishop and Fr. Kirby was appointed bishop of Clonfert. His episcopal ordination was on Saturday April 9th, 1988. He is a member of the Episcopal Commission for Justice and Peace and he is Chairman of the executive committee of Trócaire, the Irish Catholic Agency for Third World Development.