A native of London, Ontario, Bishop William T. McGrattan was born on September 19, 1956. He was ordained to the priesthood on May 2, 1987.
His Excellency received his undergraduate degree in Chemical Engineering at the University of Western Ontario, followed by a Master of Divinity from St. Peter's Seminary in London. After three years of service at St. Joseph's Parish in Chatham following his ordination, Bishop McGrattan continued his studies in theology at the Pontifical Gregorian University in Rome, where he received a Licentiate in Fundamental Moral Theology in 1992. He served on the faculty of St. Peter's Seminary in London as an associate professor, vice-rector and dean of theology, and was appointed as rector of the seminary in 1997.
In 2009, Pope Emeritus Benedict XVI appointed Bishop McGrattan as Auxiliary Bishop of Toronto and Titular Bishop of Furnos Minor. He was ordained to the episcopate on January 12, 2010. Bishop McGrattan's episcopal motto, "Habe Fiduciam in Domino" (Trust in the Lord) is taken from Proverbs 3:5, which reads "Trust in the Lord with all your heart and do not rely on your own insight."
He was appointed 12th bishop of the Diocese of Peterborough, Ontario on April 8, 2014. On January 4, 2017, Bishop McGrattan was appointed by Pope Francis to succeed Bishop Frederick Henry as the 8th bishop of the Diocese of Calgary. He was installed on February 27, 2017.
- May 2, 1987 Ordained to the priesthood
- 1987-1990 Associate Pastor at St. Joseph's Parish, Chatham, ON
- 1992 Received a Licentiate in Fundamental Moral Theology from the Pontifical Gregorian University in Rome, Italy
- 1992-1997 Served as associate professor, vice-rector, and dean of theology at St. Peter's Seminary
- 1997-2009 Rector of St. Peter's Seminary
- November 6, 2009 Appointed Auxiliary Bishop of Toronto and Titular Bishop of Furnos Minor
- January 12, 2010 Episcopal Ordination at St. Peter's Cathedral in London, ON
- April 8, 2014 Appointed Bishop of Peterborough, ON
- June 23, 2014 Installed as 12th Bishop of Peterborough, ON
- January 4, 2017 Appointed Bishop of Calgary, AB
- February 27, 2017 Installed as eighth Bishop of Calgary, AB