Prime minister, the head of government in a country with a parliamentary or semipresidential political system. In such systems, the prime minister—literally the “first,” or most important, minister—must be able to command a continuous majority in the legislature (usually the lower house in a bicameral system) to remain in office. Most countries with prime ministers have two executives, a head of government (the prime minister) and a head of state (generally either a non-executive president or a hereditary monarch).
The head of state formally appoints the prime minister, who in turn selects the other cabinet ministers. In practice, however, the choice exercised by the head of state is often quite limited (except in semipresidential systems); it is restricted generally to the head of the largest party or coalition in the legislature (typically the lower house in a bicameral system). Although the origin of the title lies in 17th-century France, where Cardinal de Richelieu was acknowledged in 1624 as principal or premier ministre, the office essentially developed in Britain in the 18th century, when the king ceased to attend and chair meetings of his ministers.
