The prime minister of Canada () is the head of government of Canada. Under the Westminster system, the prime minister governs with the confidence of a majority of the elected House of Commons; as such, the prime minister typically sits as a member of Parliament (MP) and leads the largest party or a coalition of parties. The prime minister is "called upon" by the monarch's representative, the governor general, and, as first minister, selects other ministers to form the Cabinet and chairs it. Constitutionally, the Crown exercises executive power on the advice of the Cabinet, which is collectively responsible to the House of Commons. Not outlined in any constitutional document, the office exists only per long-established convention (originating in Canada's former colonial power, the United Kingdom) that stipulates the monarch's representative, the governor general, must select as prime minister the person most likely to command the confidence of the elected House of Commons; this individual is typically the leader of the political party that holds the largest number of seats in that chamber. Canadian prime ministers are appointed to the Privy Council and styled as the Right Honourable (), a privilege maintained for life. The prime minister is supported by the Prime Minister's Office and heads the Privy Council Office. The prime minister also selects individuals for appointment as governor general (in the federal jurisdiction) and lieutenant governor (in the provinces), as well as to the Senate of Canada, Supreme Court of Canada, and other federal courts, and, as required under law, the chairs and boards of various Crown corporations. Under the Constitution Act, 1867, government power is vested in the monarch (who is the head of state), but in practice the roles of the monarch and the governor general (or the administrator) are largely ceremonial and only exercised on the advice of a Cabinet minister. Justin Trudeau is the 23rd and current prime minister of Canada. He took office on November 4, 2015, following the 2015 federal election where his Liberal Party won a majority of seats and was invited to form the 29th Canadian Ministry. Trudeau's Liberals were subsequently re-elected following the 2019 and 2021 elections with a minority of seats. Trudeau continued in office with minority governments. Origin of the office The position of prime minister is not outlined in any Canadian constitutional document and is mentioned only in a few sections of the Constitution Act, 1982,