In Canadian politics, a leadership convention is held by a political party when the party needs to choose a leader due to a vacancy or a challenge to the incumbent leader.

In Canada, leaders of a party generally remain that party's de facto candidate for Prime Minister until they die, resign, or are dismissed by the party. In the federal New Democratic Party (NDP) and some provincial NDPs, the position of party leader was treated as all other positions on the party's executive committee, and open for election at party conventions generally held every two years although incumbent leaders rarely face more than token opposition.

Usually, outgoing leaders of a Canadian political party remain as leaders until their successor is chosen at a leadership convention. However, in some circumstances, such as the death or immediate resignation of a leader, that is not possible, and an interim leader is appointed by the party for the duration of the leadership campaign.

In a few instances where a single leadership candidate has been unopposed by the entry deadline, the leadership convention has instead served as a venue for the membership to ratify the candidate. Even in such situations, however, the convention must still take place before the candidate can assume the formal and permanent leadership of the party, even if they are already serving as the party's interim leader.

Traditionally, each riding association of a party holds a special meeting to elect a fixed number of delegates to represent it at a leadership convention. These meetings would often select "alternate delegates" or "alternates", who would attend the convention but vote only if one of the delegates from the riding association was unable to attend. In addition, delegates are often selected by the party's youth and women's associations in each riding, and party associations at university and college campuses.

In addition to the elected delegates, a large number of ex officio delegates attend and vote at leadership conventions. These ex officio delegates are automatically entitled to attend by virtue of being an elected member of parliament for that party, a member of an affiliated party in a provincial legislature, a member of the party's national or provincial executive, of the executive of an affiliated women's or youth organization.

Because of the implementation of "one member one vote" (OMOV) systems and proportional delegate elections by most parties, conventions have declined in importance. In recent years, the result of the vote is either known before the convention, or the voting does not take place at the venue.

In a pure "one-member one-vote" system, each party member casts a ballot to elect the leader, and all ballots have equal weight. Modified OMOV systems may allow all members to vote but may weight the votes differently in order to ensure equality among ridings regardless of party membership or to guarantee a proportion of the vote to historically important constituencies (such as labour in the case of the NDP).