Bonar Law, in full Andrew Bonar Law, (born September 16, 1858, Kingston, New Brunswick, Canada—died October 30, 1923, London, England), prime minister of Great Britain from October 23, 1922, to May 20, 1923, the first holder of that office to come from a British overseas possession. He was the leader of the Conservative Party during the periods 1911–21 and 1922–23.

The son of a Presbyterian minister of Ulster ancestry, Law from the age of 12 was reared by wealthy cousins in Scotland. Leaving school at age 16, he eventually became a partner in a Glasgow firm of iron merchants. Elected to the House of Commons as a Conservative in 1900, he adhered to the party’s imperialist faction led by Joseph Chamberlain, whose illness (from 1906) left Law and Chamberlain’s son Austen as the leading advocates of a protective tariff. Late in 1911 the former prime minister Arthur James Balfour resigned as Conservative Party leader. The deadlock between the leading candidates for the succession, Austen Chamberlain and Walter Long, was broken by their withdrawal in favour of Law, a compromise candidate, who was elected unanimously on November 13. On that occasion and afterward, his chief adviser was his friend William Maxwell Aitken (Lord Beaverbrook from 1917), who later became a powerful newspaper publisher.

Until the outbreak of World War I, Law was concerned primarily with the tariff question and with Irish Home Rule, which, as an Ulsterman, he furiously opposed. On May 25, 1915, he became secretary for the colonies in the wartime coalition government that he had virtually forced H.H. Asquith to lead. He took part in the intrigues resulting in Asquith’s resignation on December 5, 1916. Asked by King George V to form a government, he recommended instead David Lloyd George, who assumed office the next day. In the new coalition, Law was leader of the House of Commons, a member of the war cabinet, and chancellor of the Exchequer, in which capacity he astutely managed war-loan and war-bond programs. Exchanging the chancellorship for the office of lord privy seal on January 10, 1919, he remained leader of the Commons until March 1921, when ill health forced him to resign his offices.

In 1922 the Conservatives were angered successively by a scandal over the sale of honours, the Çanak incident (when a wholly unnecessary war with Turkey seemed imminent), and a proposal that an election be called to approve a new coalition to be headed by Lloyd George. On October 19, at a party meeting in the Carlton Club, London, Law spoke against another coalition. Lloyd George at once resigned, taking with him most of the leading Tories in the government. Law then formed a Conservative government (“of the second eleven,” as Winston Churchill described it), which in November 1922 was approved by a comfortable majority of voters. The principal events of his premiership occurred in January 1923, when he almost resigned in dissatisfaction with Chancellor of the Exchequer Stanley Baldwin’s settlement of the British war debt to the United States and when he broke off diplomatic relations with France because of its occupation of the Ruhr. Aware of an inoperable malignancy in his throat, he resigned in May and was succeeded by Baldwin.