William McGrattan

On April 8, 2014, McGrattan was appointed 12th bishop of the Diocese of Peterborough, Ontario, and installed on June 23, 2014. He was appointed Bishop of Calgary, Alberta, Canada on January 4, 2017 but continued to serve as Apostolic Administrator until his successor was installed.

On 6 November 2009 McGrattan was appointed by Pope Benedict XVI as one of two new auxiliary bishops for the Archdiocese of Toronto along with Bishop Nguyen. McGrattan was ordained Titular Bishop of Furnos Minor on 12 January 2010 at St. Peter's Cathedral Basilica in London, Ontario. Bishop McGrattan took as his motto "“Habe Fiduciam in Domino” (Trust in the Lord) from Proverbs 3:5.

After ordination, Father McGrattan served three years as associate pastor at St. Joseph's Parish in Chatham, Ontario. He then continued in theology in Rome, where in 1992 he earned a Licentiate in Fundamental Moral Theology (S.T.L.) from the Pontificia Universita Gregoriana. He became a member of the faculty at St. Peter's Seminary in London, Ontario, where he served as dean of theology, becoming rector in 1997.

He was born in London, Ontario, Canada. He received a Bachelor of Engineering Science in Chemical Engineering (BESc) from the University of Western Ontario, London, Ontario in 1979. In 1987, he obtained a Master of Divinity (MDiv.) from St. Peter's Seminary. McGrattan was ordained to the priesthood on 2 May 1987 for the Diocese of London by Bishop John Michael Sherlock.

William Terrence McGrattan (born 19 September 1956) is the eighth and current Bishop of the Diocese of Calgary. He was an auxiliary bishop for the Archdiocese of Toronto and titular bishop of Furnos Minor before being appointed Bishop of the Diocese of Peterborough.