The first Roman Catholic administrative and pastoral structures established during the missionary period in the prairie west of Canada were apostolic vicariates covering vast geographical territories. Parishes, dioceses and archdioceses were formed later, when the Catholic population increased with the arrival of settlers from other parts of North America and Europe. At the time of Saskatchewan's entry into Confederation in 1905, the province was part of one large vicariate which was administered as a mission of the Diocese of St. Albert (Alberta). The Apostolic Vicariate of Saskatchewan had been erected in 1890, with Prince Albert as the see city, and Bishop Albert Pascal, OMI, had been consecrated as its first apostolic vicar in 1891. By 1905, Catholic priests, sisters and brothers were continuing to minister to First Nations and Métis, mainly in the north and central regions of Saskatchewan; by that time Catholic settlers from eastern Canada, the British Isles, western and eastern Europe, and the United States had begun the great migration to the Canadian prairie lands, bringing with them the need for Catholic parishes, schools and hospitals. As the Catholic population of the province increased, the diocesan territories were changed to meet the needs of the people.
The Vicariate of Saskatchewan became the Diocese of Prince Albert (suffragan of St. Boniface) in 1907; and a few years later the geographical territory of the diocese was reduced with the formation in 1910 of the Vicariate of Keewatin in the north, and the Diocese of Regina in the south. The Diocese of Prince Albert became a suffragan diocese of Regina in 1915 when the latter became an archdiocese; and in 1921, with the increase in the Catholic population of Saskatoon, its name was changed to Diocese of Prince Albert and Saskatoon. Also in 1921, the Benedictine Abbey of St. Peter and its surrounding parishes became the Diocese of Muenster (St. Peter's Abbacy or Abbey Nullius). The Diocese of Saskatoon was established as a separate diocese in 1933; at that time also the northern boundary of the Diocese of Prince Albert was moved to forty miles north of Green Lake to include a portion of the Diocese of Keewatin. In September 1998, diocesan boundaries were changed again, this time forming fewer dioceses with larger geographical territories. The former Diocese of Gravelbourg was amalgamated with other dioceses; most of its parishes became part of the Archdiocese of Regina, with the German-Catholic St. Joseph's Colony parishes added to the Diocese of Saskatoon. The parishes of the Abbey Nullius of Muenster were incorporated into the Diocese of Saskatoon, and a portion of the northern part of the Archdiocese of Regina was also transferred to the Saskatoon Diocese at that time.
Saskatchewan Roman Catholics are currently in the care of five dioceses: three full dioceses in southern Saskatchewan (Regina, Prince Albert and Saskatoon), with the Archdiocese of Regina as the metropolitan see; and two regions in northern Saskatchewan, which are part of dioceses in Manitoba and the Northwest Territories.
The Archdiocese of Regina has been served over the years by the following archbishops: Olivier-Elzéar Mathieu (bishop 1911-15/archbishop 1915- 29); James McGuigan (1930-34); Peter Monahan (1935-47); Michael Cornelius O'Neill (1947-73); Charles Halpin (1973-94); and Peter Mallon (1995-).
The Diocese of Prince Albert has been in the care of bishops Albert Pascal, OMI (apostolic vicar 1891-1907; bishop 1907-20); Joseph-Henri Prud'homme (bishop of Prince Albert and Saskatoon 1921-33; bishop of Prince Albert 1933- 37); Reginald Duprat (1938-52); Leo Blais (1952- 59); Laurent Morin (1959-83); and Blaise Morand (1983-).
The Diocese of Saskatoon has had six bishops: Gerald Murray, CSsR (1934-44), Philip Pocock (1944-51), Francis Klein (1952-67), James Mahoney (1967-95), James Weisgerber (1996- 2000), and Albert LeGatt (2001-).
The Diocese of Gravelbourg was served by seven bishops: Jean Villeneuve, OMI (1930-31), Louis Melanson (1932-36), Joseph Guy, OMI (1937-42), Joseph Lemieux, OP (1944-53), Aimé Décosse (1953-73), Noel Delaquis (1973-95); and Raymond Roussin, SM (1995-98).
During the period that St. Peter's Abbacy was an Abbey Nullius, it was served by the following abbots-ordinary: Michael Ott, OSB (1921-26), Severinus Gertken, OSB (1926-60), Jerome Weber, OSB (1960-90), and Peter Novecosky, OSB (1990-98).
The territories of two northern dioceses have portions of Saskatchewan under their jurisdiction: Keewatin-LePas Archdiocese (The Pas, MB) and Mackenzie-Fort Smith Diocese (Yellowknife, NT). The present bishop of Mackenzie-Fort Smith is Denis Croteau, OMI (1986-), and the archbishop of Keewatin-Le Pas is Peter Sutton, OMI (1986-).