Australian House of Representatives

The Australian House of Representatives is one of the two Houses (chambers) of the Parliament of Australia. It is referred to as the lower house, with the Senate being referred to as the upper house. The term of members of the House of Representatives is a maximum of three years from the date of the first sitting of the House, but on only one occasion since Federation has the maximum term been reached. The House is almost always dissolved earlier, usually alone but sometimes in a double dissolution of both Houses. Elections for members of the House of Representatives are often held in conjunction with those for the Senate. A member of the House may be referred to as a "Member of Parliament" ("MP" or "Member"), while a member of the Senate is usually referred to as a "Senator". The government of the day and by extension the Prime Minister must achieve and maintain the confidence of this House in order to gain and remain in power.

The House of Representatives currently consists of 150 members, elected by and representing single member districts known as electoral divisions (commonly referred to as "electorates" or "seats"). The number of members is not fixed but can vary with boundary changes resulting from electoral redistributions, which are required on a regular basis. The most recent overall increase in the size of the House, which came into effect at the 1984 election, increased the number of members from 125 to 148. It reduced to 147 at the 1993 election, returned to 148 at the 1996 election, has been 150 since the 2001 election, and will increase to 151 at the next Australian federal election.

Each division elects one member using full-preference Instant-runoff voting. This was put in place after the 1918 Swan by-election, which Labor unexpectedly won with the largest primary vote and the help of vote splitting in the conservative parties. The Nationalist government of the time changed the lower house voting system from first-past-the-post to full-preference preferential voting, effective from the 1919 general election. This system has remained in place since, allowing the Coalition parties to safely contest the same seats.