The Archdiocese of Ottawa–Cornwall (Latin: Archidioecesis Ottaviensis–Cornubiensis, French: L'Archidiocèse d'Ottawa-Cornwall) is a Catholic archdiocese that includes part of the Province of Ontario and includes the suffragan dioceses of Hearst, Pembroke, and Timmins. On 6 May 2020, Pope Francis amalgamated the Archdiocese of Ottawa and the Diocese of Alexandria-Cornwall to create the Archdiocese of Ottawa–Cornwall.

The Diocese of Bytown was erected on 25 June 1847. Its name was changed to the Diocese of Ottawa on 14 June 1860. It was elevated to archdiocese status on 8 June 1886. As of 2004, the archdiocese contained 111 parishes, 177 active diocesan priests, 102 religious priests, and 400,000 Catholics. It also has 848 Women Religious, 147 Religious Brothers, and 60 permanent deacons.

Bishops and archbishops of Ottawa

• Joseph-Eugène-Bruno Guigues (1847–1874)
• Joseph-Thomas Duhamel (1874–1909)
• Charles-Hughes Gauthier (1910–1922)
• Joseph-Médard Émard (1922–1927)
• Joseph-Guillaume-Laurent Forbes (1928–1940)
• Alexandre Vachon (1940–1953)
• Marie-Joseph Lemieux (1953–1966), appointed titular Archbishop and nuncio
• Joseph-Aurèle Plourde (1967–1989)
• Marcel André J. Gervais (1989–2007)
• Terrence Prendergast, S.J. (2007–2020)

Archbishops of Ottawa-Cornwall

• Terrence Prendergast, S.J. (May 2020–Dec 2020)
• Marcel Damphousse (2020– )

• Alexandre Vachon (1939-1940)
• Marcel André J. Gervais (1989)
• Marcel Damphousse (2020- )

• Maxime Tessier (1951-1953), appointed Coadjutor Bishop of Timmins, Ontario
• Paul-Émile Charbonneau (1960-1963), appointed Bishop of Hull, Québec
• Joseph Raymond Windle (1960-1969), appointed Coadjutor Bishop of Pembroke, Ontario
• René Audet (1963-1968), appointed Bishop of Joliette, Québec
• John Michael Behan (1977-1988)
• Gilles Bélisle (1977-1993)
• Brendan Michael O'Brien (1987-1993), appointed Bishop of Pembroke, Ontario
• Paul Marchand, SSM (1993-1999), appointed Bishop of Timmins, Ontario
• Frederick Joseph Colli (1994-1999), appointed Bishop of Thunder Bay, Ontario
• Christian Riesbeck, CC (2014-2019), appointed Bishop of Saint John, New Brunswick
• Yvan Mathieu, s.m., (2022- )

• John Thomas McNally, appointed Bishop of Calgary, Alberta in 1913
• François-Xavier Brunet, appointed Bishop of Mont-Laurier, Québec in 1913
• Joseph Charbonneau, appointed Bishop of Hearst, Ontario in 1939
• Jean Gratton, appointed Bishop of Mont-Laurier, Québec in 1978
• Jean-Louis Plouffe, appointed Auxiliary Bishop of Sault Sainte Marie, Ontario in 1986
• José Avelino Bettencourt, appointed nuncio and titular Archbishop in 2018

• Brunet, François-Xavier (1911). "Archdiocese of Ottawa" . In Herbermann, Charles (ed.). Catholic Encyclopedia. Vol. 11. New York: Robert Appleton Company.
• Archdiocese of Ottawa page at catholichierarchy.org retrieved July 13, 2006
• Carrière, Gaston (1972). "Guigues, Joseph-Bruno". In Hayne, David (ed.). Dictionary of Canadian Biography. Vol. X (1871–1880) (online ed.). University of Toronto Press.
• Perin, Roberto; Comeau-Vasilopoulos, Gayle M. (1994). "Duhamel, Joseph-Thomas". In Cook, Ramsay; Hamelin, Jean (eds.). Dictionary of Canadian Biography. Vol. XIII (1901–1910) (online ed.). University of Toronto Press.

• Archdiocese of Ottawa site

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