Herbert Henry Asquith, 1st Earl of Oxford and Asquith, (12 September 1852 15 February 1928), generally known as H. H. Asquith, was a British statesman and Liberal Party politician who served as Prime Minister of the United Kingdom from 1908 to 1916. He was the last Liberal prime minister to command a majority government, and the most recent Liberal to have served as Leader of the Opposition. He played a major role in the design and passage of major liberal legislation and a reduction of the power of the House of Lords. In August 1914, Asquith took Great Britain and the British Empire into the First World War. During 1915, his government was vigorously attacked for a shortage of munitions and the failure of the Gallipoli Campaign. He formed a coalition government with other parties but failed to satisfy critics and was forced to resign in December 1916, and never regained power.

After attending Balliol College, Oxford, he became a successful barrister. In 1886 he was the Liberal candidate for East Fife, a seat he held for over thirty years. In 1892 he was appointed as Home Secretary in Gladstone's fourth ministry, remaining in the post until the Liberals lost the 1895 election. In the decade of opposition that followed Asquith became a major figure in the party, and when the Liberals regained power under Sir Henry Campbell-Bannerman in 1905 Asquith was named Chancellor of the Exchequer. In 1908 Asquith succeeded him as prime minister. The Liberals were determined to advance their reform agenda. An impediment to this was the House of Lords, which rejected the People's Budget of 1909. Meanwhile, the South Africa Act 1909 passed. Asquith called an election for January 1910, and the Liberals won, though were reduced to a minority government. After another general election in December 1910, he gained passage of the Parliament Act 1911, allowing a bill three times passed by the Commons in consecutive sessions to be enacted regardless of the Lords. Asquith was less successful in dealing with Irish Home Rule. Repeated crises led to gun running and violence, verging on civil war.

When Britain declared war on Germany in response to the German invasion of Belgium, high-profile domestic conflicts were suspended regarding Ireland and women's suffrage. Asquith was more of a committee chair than a dynamic leader. He oversaw national mobilization, the dispatch of the British Expeditionary Force to the Western Front, the creation of a mass army, and the development of an industrial strategy designed to support the country's war aims. The war became bogged down and the demand rose for better leadership. He was forced to form a coalition with the Conservatives and Labour early in 1915. He was weakened by his own indecision over strategy, conscription, and financing. Lloyd George replaced him as prime minister in December 1916. They became bitter enemies and fought for control of the fast-declining Liberal Party. His role in creating the modern British welfare state (19061911) has been celebrated, but his weaknesses as a war leader and as a party leader after 1914 have been highlighted by historians. He remained the only Prime Minister between 1827 and 1979 to serve more than eight consecutive years in a single term.

The Liberal Party was one of the two major political parties in the United Kingdom with the opposing Conservative Party in the 19th and early 20th centuries. The party arose from an alliance of Whigs and free trade–supporting Peelites and the reformist Radicals in the 1850s. By the end of the 19th century, it had formed four governments under William Gladstone. Despite being divided over the issue of Irish Home Rule, the party returned to government in 1905 and then won a landslide victory in the following year's general election.

Under prime ministers Henry Campbell-Bannerman (1905–1908) and H. H. Asquith (1908–1916), the Liberal Party passed the welfare reforms that created a basic British welfare state. Although Asquith was the party's leader, its dominant figure was David Lloyd George. Asquith was overwhelmed by the wartime role of coalition prime minister and Lloyd George replaced him as prime minister in late 1916, but Asquith remained as Liberal Party leader. The pair fought for years over control of the party, badly weakening it in the process. In The Oxford Companion to British History, historian Martin Pugh argues:

Lloyd George made a greater impact on British public life than any other 20th-century leader, thanks to his pre-war introduction of Britain's social welfare system (especially medical insurance, unemployment insurance, and old-age pensions, largely paid for by taxes on high incomes and on the land). Furthermore, in foreign affairs, he played a leading role in winning the First World War, redrawing the map of Europe at the peace conference, and partitioning Ireland.

The government of Lloyd George was dominated by the Conservative Party, which finally deposed him in 1922. By the end of the 1920s, the Labour Party had replaced the Liberals as the Conservatives' main rival. The Liberal Party went into decline after 1918 and by the 1950s won as few as six seats at general elections. Apart from notable by-election victories, its fortunes did not improve significantly until it formed the SDP–Liberal Alliance with the newly formed Social Democratic Party (SDP) in 1981. At the 1983 general election, the Alliance won over a quarter of the vote, but only 23 of the 650 seats it contested. At the 1987 general election, its share of the vote fell below 23% and the Liberals and Social Democratic Party merged in 1988 to form the Liberal Democrats. A splinter group reconstituted the Liberal Party in 1989.

Prominent intellectuals associated with the Liberal Party include the philosopher John Stuart Mill, the economist John Maynard Keynes and social planner William Beveridge. Winston Churchill authored Liberalism and the Social Problem (1909), praised by Henry William Massingham as "an impressive and convincing argument" and widely considered as the movement’s bible.