The Office of the Prime Minister (commonly called the prime minister's office or PMO comprises the staff that supports the prime minister of Canada and is located in the Office of the Prime Minister and Privy Council Building in Ottawa, Ontario. The PMO provides policy advice, information gathering, communications, planning, and strategizing. It should not be confused with the Privy Council Office, which is the higher office that controls the Public Service of Canada and is expressly non-partisan; the PMO is concerned with making policy, whereas the PCO is concerned with executing the policy decisions made by the government.

The prime minister of Canada is the head of government of Canada. Not outlined in any constitutional document, the office exists only per long-established convention. 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 appointed by the monarch's representative, the governor general, and, as first minister, selects other ministers to form the Cabinet and chairs it. Constitutionally, executive authority is vested in the monarch, but, in practice, the powers of the monarch and governor general are nearly always exercised on the advice of the Cabinet, which is collectively responsible to the House of Commons. Canadian prime ministers are appointed to the Privy Council and styled as the Right Honourable, a privilege maintained for life.