2017 New Democratic Party leadership election

In 2017, the New Democratic Party held a leadership election to choose a successor to Tom Mulcair. The election was triggered by Mulcair having lost a leadership review at the party's federal convention held in Edmonton, Alberta, on April 10, 2016, which resulted in a majority of delegates voting in favor of holding a new leadership election. Mulcair declined to partake in the subsequent leadership election and stated that he would remain leader until the party chose a replacement.

Four candidates were on the leadership ballot: Charlie Angus, Niki Ashton, Guy Caron, and Jagmeet Singh. The voting process occurred on Sunday, October 1, 2017. Every party member was entitled to cast a secret vote in the leadership election using either a ranked ballot and Instant-runoff voting, or potentially repeated rounds of voting under exhaustive voting, with each member being able to choose one format or the other for their vote. Had no candidate received a majority of votes in the first round of voting, the least-popular candidate would have been dropped and an additional vote count held once a week until October 15, 2017 or until a candidate received a majority of votes.

Singh, the only non-MP in the race, formally announced his candidacy for the leadership on May 15, 2017. Singh received the support of 11 MPs, the most of any candidate, including former leadership candidates Nathan Cullen and Peter Julian, in addition to the support of major labour unions such as the United Food and Commercial Workers. Media attention surrounding his campaign noted the fact that, if elected, Singh would be the first visible minority person to lead a major federal party, as well as the first of the Sikh faith.

Singh was elected in the first round, with 53.8% of the votes, thus rendering the need for subsequent rounds of voting unnecessary. Following his election as leader, Singh appointed former leadership rival Guy Caron to serve as the New Democratic Party's Parliamentary Leader.