The 1918 United Kingdom general election was called immediately after the Armistice with Germany which ended the First World War, and was held on Saturday, 14 December 1918. The governing coalition, under Prime Minister David Lloyd George, sent letters of endorsement to candidates who supported the coalition government. These were nicknamed "Coalition Coupons", and led to the election being known as the "coupon election". The result was a massive landslide in favour of the coalition, comprising primarily the Conservatives and Coalition Liberals, with massive losses for Liberals who were not endorsed. Nearly all the Liberal MPs without coupons were defeated, including party leader H. H. Asquith.

The United Kingdom was a leading Allied Power during the First World War of 1914–1918. They fought against the Central Powers, mainly Germany. The armed forces were greatly expanded and reorganised—the war marked the founding of the Royal Air Force. The highly controversial introduction, in January 1916, of conscription for the first time in British history followed the raising of one of the largest all-volunteer armies in history, known as Kitchener's Army, of more than 2,000,000 men. The outbreak of war was a socially unifying event. Enthusiasm was widespread in 1914, and was similar to that across Europe.