The House of Representatives is the sole chamber of the New Zealand Parliament. The House passes laws, provides ministers to form the Cabinet, and supervises the work of government. It is also responsible for adopting the state's budgets and approving the state's accounts.

The House of Representatives is a democratic body consisting of representatives known as members of parliament (MPs). There are normally 120 MPs, though there are currently 123 due to an overhang. Elections take place usually every three years using a mixed-member proportional representation system, which combines first-past-the-post elected seats with closed party lists. 72 MPs are elected directly in single-member electoral districts and further seats are filled by list MPs based on each party's share of the party vote. A government may be formed from the single party or coalition of parties that has the support of a majority of MPs. If no majority is possible, a minority government can be formed with a confidence and supply arrangement. If a government is unable to maintain the confidence of the House then an early general election can be called.

The House of Representatives was created by the New Zealand Constitution Act 1852 (effective 1853), an act of the British Parliament, which established a bicameral legislature; the upper chamber, the Legislative Council, was abolished in 1950. Parliament received full control over all New Zealand affairs in 1947 with the passage of the Statute of Westminster Adoption Act. The debating chamber of the House of Representatives is located inside Parliament House in Wellington, the capital city. Sittings of the House are usually open to the public, but the House may at any time vote to sit in private. Proceedings are broadcast through Parliament TV and the AM Network.

The New Zealand House of Representatives takes the British House of Commons as its model. The New Zealand Parliament is based, in practice, on the Westminster system (that is, the procedures of the British Parliament). As a democratic institution, the primary role of the House of Representatives is to provide representation for the people and to pass legislation on behalf of the people (see § Passage of legislation).

The House of Representatives also plays an important role in responsible government. The New Zealand Government (that is, the executive), directed by the Cabinet, draws its membership exclusively from the House. A government is formed when a party or coalition can show that it has the "confidence" of the House, meaning the support of a majority of members of parliament. This can involve making agreements among several parties. Some may join a coalition government, while others may stay outside the government but agree to support it on confidence votes. The prime minister (leader of the government) is answerable to, and must maintain the support of, the House of Representatives; thus, whenever the office of prime minister falls vacant, the governor-general appoints the person who is most likely to command the support of the House. If the House of Representatives loses confidence in the Cabinet, and therefore in the government, then it can dissolve the government if a vote of no-confidence is passed.

The House of Representatives normally consists of 120 members, who bear the title "Member of Parliament" (MP). They were previously known as "Members of the House of Representatives" (MHRs) until the passing of the Parliamentary and Executive Titles Act 1907 when New Zealand became a Dominion, and even earlier as "Members of the General Assembly" (MGAs).

All MPs are democratically elected, and usually enter the House following a general election. Once sworn in, MPs normally continue to serve until the next dissolution of parliament and subsequent general election, which must take place at least every three years. Early general elections (sometimes termed "snap elections") are possible at the discretion of the prime minister, especially if a minority government is unable to retain the confidence of the House. Members who change their party allegiance during a term—known as "waka-jumping"—may be expelled from the House. Members may also be expelled in cases of criminal activity or other serious misconduct. Some expulsions have been challenged through the courts. Casual vacancies in electorates are filled through by-elections; if a list member's seat becomes vacant then the next available person on their party's list is appointed to the position. List MPs are free to stand in electorate by-elections and in the case of successful contest their own seat will be filled 'in turn'.

To be an MP a person must be a New Zealand citizen (by birth or naturalisation) at the time of the election and not be disqualified from enrolling to vote; unlike certain other countries, bankruptcy is not grounds for disqualification from office. Party list candidates are always nominated by political parties.