By elections to the 42nd Canadian Parliament

Medicine Hat—Cardston—Warner

A by-election was held on October 24, 2016 in the riding of Medicine Hat—Cardston—Warner, which had been vacant since March 23, 2016 when Conservative Party of Canada MP Jim Hillyer died in his office following a heart attack. The riding has been held by centre-right parties since Bert Hargrave defeated Liberal incumbent Bud Olson, himself a former Social Credit MP, in 1972. This was the first by-election in the 108-year history of the Medicine Hat constituency. The Speaker's warrant regarding the vacancy was received on March 24, 2016.

Retired Medicine Hat Police inspector Glen Motz defeated businessman Brian Benoit, former Cardston-Taber-Warner and Calgary-Glenmore MLA Paul Hinman, lawyer Michael W. Jones, and party worker Joe Schow for the Conservative nomination, which was held in late June. Cypress-Medicine Hat MLA Drew Barnes, former Medicine Hat MLA Blake Pedersen, and Dan Hein, Hillyer's closest competitor for the nomination in 2015, all declined to run for the Conservative nomination despite speculation to the contrary.

Well-known Medicine Hat businessman Stan Sakamoto was the Liberal candidate.

The Libertarian Party of Canada nominated Sheldon Johnston as its candidate. The Libertarians and the Rhinoceros Party nominated candidates for the first time in Medicine Hat.

Ottawa—Vanier

A by-election will be held on April 3, 2017 in the riding of Ottawa—Vanier, which has been vacant since the death of Mauril Bélanger on August 16, 2016 from amyotrophic lateral sclerosis (also known as Lou Gehrig's disease). The riding is one of the most solidly Liberal in the country, having elected Liberals both federally and provincially in every election since its creation in 1935. The Speaker's warrant regarding the vacancy was received on August 23, 2016.

After several prominent potential candidates, including Bélanger's widow Catherine Bélanger, Ottawa councillors Tobi Nussbaum and Tim Tierney, and 2014 council candidate Catherine Fortin LeFaivre declined to run, eight candidates sought the Liberal nomination: Senate staffer Khatera Akbari, lawyer Jean Claude Dubuisson, communications consultant Mona Fortier, Liberal staffer Eric Khaiat, former Cape Breton Highlands—Canso MP Francis LeBlanc, public servant Ainsley Malhotra, former executive director of The Humanitarian Coalition Nicolas Moyer, and Unique FM executive director Véronique Soucy. Up to 6,500 party members were eligible to vote in the nomination contest. Mona Fortier won the nomination on February 5, 2017.

Unsuccessful 2015 candidate Emilie Taman, a University of Ottawa law professor and daughter of former Supreme Court Justice Louise Arbour, will run again for the NDP.

Parliament Hill staffer Adrian Papara defeated former New Brunswick MLA Joel Bernard for the Conservative Party nomination, decided on February 16.

Educator and community activist Nirmala Dookeran is the Green candidate.

Calgary Heritage

The riding of Calgary Heritage became vacant when former Prime Minister of Canada Stephen Harper resigned his seat on August 26, 2016 in order to return to private life, including accepting directorships on corporate boards and establishing a consultancy firm. The electoral district was created for the 2015 federal election and has had Harper as its only MP; however, it is largely composed of the former riding of Calgary Southwest which was held by conservative parties throughout its existence.

Bob Benzen, a small business owner and current member of the Calgary Heritage Conservative Association defeated Rick Billington, a lawyer and the former president of the Calgary Heritage Conservative Association, and city prosecutor Paul Frank for the Conservative nomination, which was decided on October 23. Former Calgary Centre MP Joan Crockatt, party insider Alan Hallman, former Medicine Hat MP Monte Solberg, and Dan Williams, a former staffer to Calgary Midnapore MP Jason Kenney, all declined to run for the nomination despite speculation to the contrary. Ric McIver, leader of the Progressive Conservative Association of Alberta and MLA for Calgary-Hays, stated that he would not run.

Rumoured candidates for the Liberal nomination included physician Brendan Miles, the 2015 candidate in this riding, Chima Nkemdirim, the chief of staff to Calgary Mayor Naheed Nenshi, and former Conservative MP Lee Richardson. On February 8, 2017, the Liberal nomination was won by physician Scott Forsyth, defeating Steven Turner and Kanwar Gill.

Khalis Ahmed won the uncontested NDP nomination.

Taryn Knorren defeated Brennan Wauters for the Green Party of Canada nomination.

The Libertarian candidate was Darcy Gerow.

Businesswoman and former Dragons' Den star Arlene Dickinson was considered a potential candidate until she declined interest on January 22. Dickinson stated she had supported aspects of both Conservative and Liberal policies in the past, but considers herself non-partisan.

The by-election, being held on April 3, 2017, was announced on February 22, 2017. The Speaker's warrant regarding the vacancy was received on August 29, 2016. The last day a by-election could have been announced was February 25, 2017, with an election held at least 36 days after being announced.

Calgary Midnapore

The riding of Calgary Midnapore was vacated by Conservative MP Jason Kenney who resigned his seat effective September 23, 2016 in order to seek the leadership of the Progressive Conservative Association of Alberta. The electoral district was created for the 2015 federal election and has had Kenney as its only MP, however predecessor ridings from which Calgary Midnapore was created had, since the 1993 federal election, successively elected Reform, Canadian Alliance and Conservative MPs.

Ryan Zedic was acclaimed as the Green Party of Canada candidate on December 8, 2016.

Former diplomat Stephanie Kusie defeated local riding association president Jack Redekop for the Conservative nomination, held on January 14, 2017.

Haley Brown was acclaimed as the Liberal candidate on January 22.

Holly Heffernan was acclaimed as the NDP candidate on February 6.

The by-election, being held on April 3, 2017, was announced on February 22, 2017. The Speaker's warrant regarding the vacancy was received on September 23, 2016. The last day a by-election could have been announced was March 22, 2017, with an election held at least 36 days afterwards.

Markham—Thornhill

The riding of Markham—Thornhill was vacated on February 1, 2017, following the appointment of Liberal MP and Minister of Immigration, Refugees, and Citizenship John McCallum as Ambassador to China. The electoral district was created for the 2015 federal election and has had McCallum as its only MP, however McCallum had represented predecessor ridings from which Markham—Thornhill was created since the 2000 federal election.

Technology entrepreneur Afraj Gill, School trustee Juanita Nathan, Justin Trudeau's director of appointments and former Queen's Park staffer Mary Ng, and former city council candidate Nadeem Qureshi are running for the Liberal Party nomination, to be decided March 4, 2017. Ontario cabinet minister and Markham—Unionville MPP Michael Chan, 2015 Markham—Unionville Liberal candidate Bang-Gu Jiang, businesswoman Sofia Sun, and former city councillor Khalid Usman were rumoured to be possible candidates but have endorsed Ng. Other possible candidates for the Liberal nomination include Markham Regional councillor Jack Heath and Markham Mayor Frank Scarpitti. On January 23, Heath announced that he would not run for the nomination.

Banker Theodore Antony is seeking the Conservative Party nomination.

Small business owner Gregory Hines is seeking the NDP nomination. Hines previously ran for the party in Markham—Stouffville in 2015.

Liberal nomination contestant Nadeem Qureshi has stated that he may run as an independent candidate in the by-election in protest of the Liberal Party's handling of their nomination process.

The by-election, being held on April 3, 2017, was announced on February 22, 2017. The Speaker's warrant regarding the vacancy was received on February 6, 2017; under the Parliament of Canada Act the writ for the by-election had to be issued no earlier than February 17, 2017 and no later than August 5, 2017. The election date must be set to be a Monday at least 36 days after the writ is issued.

Saint-Laurent

The riding of Saint-Laurent was vacated on February 6, 2017, following the appointment of Liberal MP and former Minister of Foreign Affairs Stéphane Dion as Canada's Ambassador to the European Union and Germany. The riding (previously called Saint-Laurent—Cartierville) has been represented by Dion since 1996, and has been held by the Liberals since its creation in 1988.

Candidates for the Liberal nomination include former Nelligan MNA and provincial cabinet minister Yolande James, and tax law professor Marwah Rizqy, the 2015 Liberal candidate in Hochelaga. Saint-Laurent Borough Mayor and Montreal City Councillor Alan DeSousa intended to run for the nomination but was rejected by the party's nomination committee.

Conservative leadership candidate and venture capitalist Rick Peterson is running for the Conservative nomination.

Deputy Leader Daniel Green will be the Green Party candidate.

The by-election, being held on April 3, 2017, was announced on February 22, 2017. The Speaker's warrant regarding the vacancy was received on February 8, 2017; under the Parliament of Canada Act the writ for the by-election had to be issued no earlier than February 19, 2017 and no later than August 7, 2017. The election date must be set to be a Monday at least 36 days after the writ is issued.