The first Prime Minister of the United Kingdom was Sir Robert Walpole, who served from April 4, 1721, to February 11, 1742. Often regarded as the first to hold the office in its modern sense, Walpole was appointed as First Lord of the Treasury and effectively became the leader of the government under King George I and George II. While the title “Prime Minister” wasn’t officially used at the time, Walpole’s role in coordinating government policy and managing the House of Commons set the precedent for the position. His tenure, lasting over 20 years, remains the longest of any UK Prime Minister.