By-elections to the 44th Canadian Parliament

The riding of Mississauga—Lakeshore was vacated on May 27, 2022 following the resignation of Liberal MP Sven Spengemann to accept a position with the United Nations.[2] Spengemann had represented the riding since 2015, when he defeated Conservative incumbent Stella Ambler.

Running for the Liberals is former MPP Charles Sousa, who represented the area provincially from 2007 to 2018 and previously served in the provincial cabinets of Dalton McGuinty and Kathleen Wynne, including as Minister of Finance from 2013 to 2018.[13][14][15] Alex Crombie, a former Queen's Park staffer and son of Mississauga mayor Bonnie Crombie, was seen as a potential candidate prior to Sousa's nomination.[16]

Running for the Conservatives is Ron Chhinzer, a police officer.[14] Michael Ras, who finished second to Spengemann in 2021, considered running for the nomination before declining.[13]

The NDP has nominated Julia Cole, who ran for the seat's provincial counterpart in the provincial election earlier in the year, while running for the Greens is Mary Kidnew, a past president of the Hillcrest Ratepayers Association.[14][17]

Rhinoceros Party leader Sébastien CoRhino will contest the by-election.[18] As well, the Rhinoceros Party organized a protest against the Trudeau government's abandonment of electoral reform in 2017 by running thirty-two independent candidates, breaking their own record for most candidates nominated in a single riding in Canada, previously set in the riding of Saint Boniface—Saint Vital in the 2021 Canadian federal election.[19]

The riding of Winnipeg South Centre was vacated on December 12, 2022 following the death of Liberal MP and former cabinet minister Jim Carr.[3] Carr had represented the riding since 2015, when he defeated Conservative incumbent Joyce Bateman, and had been battling multiple myeloma and kidney failure since 2019. Carr also defeated Bateman in rematches in 2019 and 2021.

Running for the Liberals is Carr's son Ben, an educator and former staffer to Mélanie Joly.[22][23][24] Winnipeg city councillor Sherri Rollins briefly ran for the nomination before withdrawing and throwing her support behind Carr.[25][26]

The Conservatives have nominated Damir Stipanovic, an air traffic controller and member of the Royal Canadian Air Force Reserve.[24]

Running again after previously running in 2021 are NDP candidate Julia Riddell, a clinical psychologist, and Green candidate Doug Hemmerling, a local educator.[24]

The riding of Oxford was vacated on January 28, 2023, following the resignation of Conservative MP Dave MacKenzie, who had held the seat since 2004.[5]

Arpan Khanna, the party's national outreach chair and 2019 candidate in Brampton North[27] defeated Woodstock city-county councillor Deb Tait, MacKenzie's daughter and former ministerial staffer Rick Roth for the Conservative nomination.[28][29] Gerrit Van Dorland, executive assistant to Cypress Hills—Grasslands MP Jeremy Patzer was running for the nomination until he was disqualified by the Conservatives over a dispute about whether he disclosed information to the party.[30] In February 2023, MacKenzie accused the party of supporting Khanna, which he argues is a violation of the party nomination rules based on the Conservative's code of conduct, during the race.[31][32]

Running for the Liberals is local realtor, former educator, and past Woodstock mayoral candidate David Hilderley.[33][34] Citing concerns with the Conservative nomination process, previous MP Dave MacKenzie endorsed Hilderley in April 2023.[33]

Western University professor Cody Groat defeated Matthew Chambers, the party candidate for the riding in the 2019 and 2021 elections for the NDP nomination.[35][36]

The riding of Portage—Lisgar was vacated on February 28, 2023, following the resignation of Conservative MP Candice Bergen.[37][38] Bergen, a cabinet minister in the government of Stephen Harper and the interim leader of the Conservative Party and Leader of the Opposition from February to September 2022, had held the seat since 2008.

Bergen's former campaign manager Branden Leslie defeated Rejeanne Caron, the party's 2019 candidate in Saint Boniface—Saint Vital and 2021 candidate in Elmwood—Transcona; Winkler resident Don Cruickshank,[39] Morden-Winkler MLA and former Progressive Conservative Party of Manitoba cabinet minister Cameron Friesen;[40] and Lawrence Toet, the MP for Elmwood—Transcona from 2011 to 2015 for the Conservative nomination.[6][41][42] Liz Reimer, a Progressive Conservative Party of Manitoba staffer and former assistant to Friesen, and Josh Okello were previously running for the nomination, however after Friesen announced his campaign they withdrew their bids in order to run for the Progressive Conservative nomination in Morden-Winkler.[43][44][45]

Maxime Bernier, who is the former MP Beauce and the current leader of the People's Party of Canada, announced on May 12, 2023, that he would run for the seat.[46][47][48]

The Liberals announced Kerry Smith as their candidate on May 13.[49]

The riding of Notre-Dame-de-Grâce—Westmount was vacated on March 8, 2023, following the resignation of Liberal MP Marc Garneau.[8] Garneau, previously the Minister of Transport and Minister of Foreign Affairs in the government of Justin Trudeau, had held the seat since 2008.

Running for the Liberals is Anna Gainey, former president of the party and daughter of former Montreal Canadiens General Manager Bob Gainey.[50][51] Gainey won the Liberal nomination on May 15, 2023, defeating Fred Headon, vice president and general counsel of Air Canada, and 2021 La Pointe-de-l'Île candidate Jonas Fadeu.[52][51]

Human rights activist and Green Party deputy leader Jonathan Pedneault was announced as the party's candidate on May 15, 2023.[53]

The riding of Calgary Heritage was vacated on December 31, 2022 following the October 20 announcement from Conservative MP Bob Benzen that he would resign his seat by the end of the year in order to return to the private sector. Benzen had held the seat since a 2017 by-election in which he was elected to replace former Prime Minister and former Conservative leader Stephen Harper.[4][54] The by-election is expected to be called following the conclusion of the 2023 Alberta general election.[55]

Shuvaloy Majumdar, global director for Harper's international consulting firm Harper & Associates defeated former parliamentary staffer Quinn Heffron for the Conservative nomination.[56][57][28]

The riding of Durham, represented by former Conservative leader Erin O'Toole, is expected to be vacated at the end of the House of Commons' spring parliamentary session, currently dated for June 23, 2023.[9] O'Toole, who led the party from 2020 to 2022 and served as Minister of Veterans Affairs in the government of Stephen Harper, has held the seat since a 2012 by-election.

Running for the Conservative nomination is Jamil Jivani, conservative commentator and president of the Canada Strong and Free Network.[58]