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.[16][17][18] 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.[19]

Running for the Conservatives is Ron Chhinzer, a police officer.[17] Michael Ras, who finished second to Spengemann in 2021, considered running for the nomination before declining.[16]

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.[17][20]

Rhinoceros Party leader Sébastien CoRhino will contest the by-election.[21] 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.[22]

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.

Carr's son Ben, an educator and former staffer to Mélanie Joly, is running for the Liberal nomination.[25][26] Winnipeg city councillor Sherri Rollins briefly ran for the nomination before withdrawing and throwing her support behind Carr.[27][28]

The NDP nominated Julia Riddell, a clinical psychologist who ran for the seat in 2021.[29]

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][30]

Shuvaloy Majumdar, global director for Harper's international consulting firm Harper & Associates defeated former parliamentary staffer Quinn Heffron for the Conservative nomination.[31][32][33]

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]

Declared candidates for the Conservative nomination include: Woodstock city-county councillor Deb Tait, MacKenzie's daughter; Arpan Khanna, the party's national outreach chair and 2019 candidate in Brampton North; former ministerial staffer Rick Roth.[33][34] 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 whether he disclosed information to the party.[35] On February 2023, MacKenzie accused the party of supporting Khanna, which he argues is a violation of the party nomination rules based on the Conservatives code of conduct, during the race.[36][37]

The riding of Portage—Lisgar was vacated on February 28, 2023 following the resignation of Conservative MP Candice Bergen.[38][39] 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.

Declared candidates for the Conservative nomination include: Rejeanne Caron, the party's 2019 candidate in Saint Boniface—Saint Vital and 2021 candidate in Elmwood—Transcona; Winkler resident Don Cruickshank,[40] Morden-Winkler MLA and former Progressive Conservative Party of Manitoba cabinet minister Cameron Friesen;[41] Bergen's former campaign manager Branden Leslie; Josh Okello,[42] Liz Reimer, a Progressive Conservative Party of Manitoba staffer and former assistant to Friesen; and Lawrence Toet, the MP for Elmwood—Transcona from 2011 to 2015.[6][43]

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.

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.