The lower chamber of the British Parliament. It began as an element of the Parliaments summoned by the king in the later 13th century: both knights of the shire and burgesses of boroughs were summoned to Simon de Montfort’s Parliament in 1265. It took over 500 years for the Commons to become supreme in the tripartite division of power between it, the House of Lords, and the monarchy. In the 14th century both Houses gained constitutional rights in relation to the monarchy; many of the struggles between Richard II and his opponents were waged through the Commons—notably in the Merciless Parliament of 1388.

In the early 17th century, when differences between the monarchy and Parliament first surfaced, the Commons took the lead in, for instance, the Petition of Right (1628), winning Charles I’s acceptance of the principle of no taxation without parliamentary assent. The Long Parliament (1640–60 abolished the House of Lords and set up the Commonwealth, and it was the Commons that was instrumental in inviting Charles II to take up the throne, just as it promoted the Bill of Rights (1689) and Act of Settlement (1701) that defined the relations between Commons, Lords, and the monarchy.

Although the Commons had gained considerable constitutional powers during the 17th century and had had some notable Prime Ministers, such as Robert Walpole and William Pitt, it was still, at the beginning of the 19th century, no more than an equal partner with the House of Lords. Extension of the franchise and the influence of such powerful members as Robert Peel, Lord Palmerston, Lord John Russell, and William Gladstone did much to extend its power, so that by the end of the century it was effectively regarded as the voice of the people. Following a series of Reform Acts and other legislation (1832, 1867, 1884, 1918, 1928, 1948, 1969) members of the House of Commons are today elected by universal adult suffrage. By the Parliament Act of 1911, the maximum duration of a Parliament became five years.

The life of a Parliament is divided into sessions, usually of one year in length. As a rule, Bills likely to raise political controversy are introduced in the Commons before going to the Lords, and the Commons claim exclusive control in respect of national taxation and expenditure. Since 1911 Members have received payment.

Members of Parliament are elected from 650 single-member constituencies in plurality (first-past-the-post) elections. The presiding officer of the Commons is an elected Speaker, who has power to maintain order and functions in a strictly non-partisan way. The House of Commons is organized along adversarial lines, its proceedings normally controlled by a disciplined party majority. The exercise by the House of Commons of its powers in matters of legislation, finance, scrutiny, and enquiry are thus in practice largely party-dominated, subject to the rights conventionally accorded to the opposition. On the other hand, an increasing role is played by all-party committees, such as standing committees, which consider and amend bills, or select committees, which monitor the workings of government departments, taking evidence, questioning witnesses, and issuing reports. Following a general election, or a change of leadership, the leader of the party commanding an overall majority in the House of Commons is invited by the monarch to become Prime Minister and form a cabinet. When no party has an overall majority, the leader of the largest party usually becomes the Prime Minister of a single-party minority government that relies on other parties’ support or abstention in crucial votes. The alternative is a formal coalition, such as that formed in 2010 between the Conservative and Liberal Democrat parties; these are very rare in peacetime.