The prime minister of Australia is the head of government of the Commonwealth of Australia. The prime minister is the chair of the Cabinet of Australia and thus the head of the federal executive government. Under the principles of responsible government, the prime minister is both responsible to and a member of the Commonwealth Parliament. The current prime minister is Anthony Albanese of the Australian Labor Party, who assumed the office on 23 May 2022.

The role and duties of the prime minister are not described by the Australian constitution but rather defined by constitutional convention deriving from the Westminster system and responsible government. The prime minister is formally appointed by the governor-general, who is ordinarily constrained by convention to choose the parliamentarian able to command the confidence of the House of Representatives (the lower house). Since Federation, this has almost always been the leader of the majority party or coalition. In practice, this means the prime minister most often changes after an election results in a different party gaining control of the lower house or as a result of the majority party changing its leader internally between elections.

The office of prime minister comes with various privileges, including the use of two official residences: The Lodge in Canberra and Kirribilli House in Sydney, as well as an office at Parliament House.

Thirty-one people (thirty men and one woman) have served as prime minister. The first was Edmund Barton, who took office on 1 January 1901 following the federation of the British colonies in Australia. The longest-serving prime minister was Robert Menzies, who served over 18 years, and the shortest-serving was Frank Forde, who served one week.

In common with other political systems based on the Westminster system, the prime minister both leads the executive government and wields significant power in Parliament.

Cabinet, the primary decision-making body of the executive government, is chaired by the prime minister. While the prime minister has been described as the "first among equals" of the other ministers that make up cabinet, they nevertheless wield primary influence in the body. They set the agenda and processes of cabinet meetings and have the final word where a collective decision cannot be reached. Ministers making up the cabinet are chosen by the prime minister and may be removed at any time. Additionally, the prime minister chooses the portfolio of each minister and a prime minister's resignation or dismissal leads by convention to the resignation of all other ministers. The precise authority of each individual prime minister within cabinet is uncertain, as their deliberations are secret. The prime minister also has the authority to make independent policy decisions independently from Cabinet, with such decisions colloquially called "captain's calls". The prime minister also has significant influence in the setting of foreign policy, through their role as chair of the National Security Committee, a sub-committee of cabinet whose decisions do not need to be endorsed by the cabinet as a whole.

The prime minister is also one of the responsible ministers for the Department of the Prime Minister and Cabinet, whose tasks include general policy development across the government, inter-governmental communications, honours and symbols policy and Indigenous programmes.

Since the emergence of the strong party system in Australia in the 1920s, prime ministers have almost always been the parliamentary leader of the party (or leader of the senior party in a coalition of parties) that has a majority in the House of Representatives (which has been either the Labor Party or the Liberal Party in coalition with the National Party since the 1940s). Responsible government has always required the prime minister and government to have the confidence of a majority of the lower house in order to govern, however the emergence of strong parties with members strongly punished for voting against party policy (also known as crossing the floor) has meant that most prime ministers and governments have significant control over the passage of bills in this house. However, bills must also be passed by the Senate (the upper house) in order to become law and the government rarely has a majority in this house, leading to some checks on the legislative powers of the government. The prime minister also controls the date of elections, through formal advice to the governor-general, with such elections usually occurring within a 6-month period prior to the maximum 3-year term of the House of Representatives expiring.