300px|thumb|[[Notre-Dame Cathedral (Ottawa)|Notre-Dame Cathedral Basilica, the oldest and largest church in Ottawa, is a National Historic Site of Canada and the central church of the Catholic Archdiocese of Ottawa-Cornwall.]]
300px|thumb|[[St. Alban's Anglican Church (Ottawa)|St. Alban's Anglican Church is Ottawa's oldest surviving church building and was attended by many of Canada's early political leaders, including Canada's first prime minister John A. Macdonald.]]
300px|thumb|[[Metropolitan Bible Church|The MET is a church in Ottawa's south end.]]
200px|thumb|[[Ste-Anne (Ottawa)|Ste-Anne Catholic Church is a rare example of Québecois church architecture in Ontario. It is home to St. Clement Parish, a Catholic community which continues to use the traditional Latin liturgy.]]
Catholic
Latin Church
Archdiocese of Ottawa-Cornwall
The Archdiocese of Ottawa-Cornwall includes several parishes outside the city limits, which have been included in the list. Francophone communities are marked with a fleur-de-lys: 15x15px.
Personal Ordinariate of the Chair of Saint Peter
- Annunciation of the Blessed Virgin Mary
Roman Catholic Military Ordinariate of Canada
- Our Lady of the Airways Chapel (see Ecumenical below)
Melkite (Greek) Catholic Church
- Saints Peter and Paul Melkite Catholic Church
Syriac Maronite Church of Antioch
- Saint Charbel Maronite Catholic Church
Syriac Catholic Church
- Saint Paul Syriac Catholic Mission
Ukrainian Greek Catholic Church
- St. John the Baptist Ukrainian Catholic Shrine
Canonically irregular groups
- Society of St Pius X Mission, meeting at the Holy Ghost Chapel.
Old Catholic Church
- Mission Parish of St. Aelred Old Roman Catholic.
Christian Science
- First Church of Christ, Scientist, designed by John Pritchard MacLaren 1913–14.
Gnostic Catholic Apostolic Church (EGCA)
- Gnostic Church of Ottawa-Gatineau
Ecumenical
Canadian Forces Support Unit Ottawa Chaplain Services
- Canadian Forces Ottawa Chapel houses "Our Lady of the Airways" Our Lady of the Airways Chapel and "Elizabeth Park Protestant Congregation". These are the ecumenical faith communities meeting in the Uplands Site chapel (337 Breadner Boulevard, Gloucester) located beside Ottawa's International Airport on the former Canadian Forces Uplands Military Base.( ) These worshiping communities are part of the Canadian Forces Support Unit Ottawa Chaplain Services and have regular Roman Catholic and Protestant services serving military members and their families in the National Capital Region. As well, there is assistance for other denominations.
Orthodox
Eastern Orthodox
American Carpatho-Russian Orthodox Diocese
- Christ the Saviour
Greek Orthodox Archdiocese of Canada
- Kimisis Tis Theotokos (Dormition of the Theotokos)
Antiochian Orthodox Christian Archdiocese of North America
- St. Elias Cathedral
- St. Elijah Antiochian Orthodox Church, built 1950. The church was sold in 1989, with the community moving to St. Elias Cathedral, and the building was converted to St. Elijah's Housing.
Orthodox Church in America
- Annunciation Cathedral
Romanian Orthodox Church
- St. Matthew
- St. Nicholas
Russian Orthodox Church Outside Russia
- Protection of the Holy Virgin Memorial Church
- St. Xenia of Petersburg
Serbian Orthodox Church
- St. Stefan
- Meeting of the Lord - Serbian Orthodox Parish (Ottawa)
Ukrainian Orthodox Church of Canada
- Assumption of the Blessed Virgin Mary Cathedral
Oriental Orthodox
Coptic Orthodox Church
- St. George and St. Anthony
- St. Mark and St. Mary of Egypt
- St. Mary
Ethiopian Orthodox Tewahedo Church
- St. Teklehaimanot
Eritrean Orthodox Church
- Kidus Gabriel
Armenian Orthodox Church
- St. Mesrob