A **prime minister** is the head of government in a parliamentary or semi-presidential system, leading the executive branch and directing government policy and administration. Unlike a head of state, who may be a monarch or president with largely ceremonial duties, the prime minister is the chief political leader responsible for running the country and commanding the confidence of the legislature. This role includes selecting cabinet ministers, setting the legislative agenda, managing the civil service, and overseeing government operations[1][2][3][6][7]. In Westminster-style systems, such as the United Kingdom, Canada, Australia, and New Zealand, the prime minister holds significant constitutional powers, including influencing economic priorities and the structure of government ministries. They may dissolve the legislature and call elections, usually by convention. The prime minister’s authority is strongest immediately following an election and can wane if the government loses popularity[1]. In other parliamentary systems, the prime minister also plays a key role in coordinating government work, chairing ministerial committees, and ensuring the implementation of government programs. For example, in Finland, the prime minister heads the Prime Minister’s Office, which manages government continuity, EU policy, and state ownership matters[8]. The current UK prime minister is Sir Keir Starmer, who took office on 5 July 2024. He has a background in law, having served as Director of Public Prosecutions and was knighted for services to criminal justice before entering politics as Labour Party leader in 2020[4]. In summary, the prime minister is the central figure in government leadership in parliamentary systems worldwide, responsible for policy direction, government administration, and maintaining parliamentary support, with specific powers and functions varying by country.