(This article is about the office of the Prime Minister of Australia. For a list of Australian Prime Ministers, see List of Prime Ministers of Australia.) The Prime Minister of the Commonwealth of Australia is the head of government in Australia. The individual who holds the office is the most senior Minister of the Crown, the leader of the Cabinet and the chairperson of the National Security Committee. The office is not mentioned in the Constitution of Australia and exists only through an unwritten political convention and tradition. Despite this, in practice it is the most powerful parliamentary position in Australia. The individual who holds the office is commissioned by the Governor-General of Australia.