Roman Catholic Diocese of Thunder Bay Tags: Clerical Administrative Region, Diocese.The Roman Catholic Diocese of Thunder Bay (Latin: Dioecesis Sinus Tonitralis) (erected 29 April 1952 as the Diocese of Fort William) is a suffragan of the Archdiocese of Toronto. It was renamed on 26 February 1970. thumbnail point Established April 29 1952 location Roman_Catholic_Diocese_of_Thunder_Bay__location__1 patron Saint Patrick province Roman Catholic Archdiocese of Toronto territory Northern Ontario latitude 48.3822 longitude -89.2494 Learn more... Loading...