The 1931 United Kingdom general election was held on Tuesday, 27 October 1931. It saw a landslide election victory for the National Government, a three-party coalition which had been formed two months previously after the collapse of the second Labour government. Journalist Ivor Bulmer-Thomas described the result as "the most astonishing in the history of the British party system".

Unable to secure support from his cabinet for his preferred policy responses to the economic and social crises brought about by the Great Depression, Prime Minister Ramsay MacDonald split from the Labour Party and formed a new national government in coalition with the Conservative Party and a number of Liberals. MacDonald subsequently campaigned for a "Doctor's Mandate" to do whatever was necessary to fix the economy, running as the leader of a new party called National Labour within the coalition. Disagreement over whether to join the new government also resulted in the Liberal Party splitting into three separate factions, including one led by former Prime Minister David Lloyd George.

Collectively, the parties forming the National Government won 67% of the popular vote and 554 (90.1%) of 615 seats in the House of Commons. Although the bulk of the National Government's support came from the Conservative Party, which won a majority in its own right with 470 seats, MacDonald remained Prime Minister. The Labour Party suffered its greatest ever defeat—losing four-fifths of its seats, including the seat of leader Arthur Henderson—and became the official opposition with just 52 MPs. The collapse of the Liberals into competing factions also ended their time as a significant force in British politics; the breakaway National Liberals were eventually absorbed into the Conservatives in 1947, while the main Liberal Party would remain in the political wilderness until its revival in the 1970s.

It is the most recent election in which any single party (the Conservatives) received an absolute majority of the votes cast, and the last UK general election not to take place on a Thursday. It was also the last election until 1997 in which any single party won more than 400 seats.

After battling with the Great Depression for two years, the Labour government of Ramsay MacDonald was faced with a budget crisis in August 1931. The cabinet deadlocked over its response, with several influential members—such as Arthur Henderson—unwilling to support budget cuts (in particular a cut in the rate of unemployment benefit) which were pressed by the civil service and opposition parties. Crucially, Chancellor of the Exchequer Philip Snowden refused to consider deficit spending or tariffs as alternative solutions, and without any other options to address the crisis the government was forced to resign. However, MacDonald was encouraged by King George V to form an all-party National Government in coalition with the Conservatives and Liberals in order to break the deadlock.

The initial hope was that the coalition government would hold office for only a few weeks in order to address the country's immediate economic crises, then dissolve for a return to ordinary party politics—but when the government was forced to remove the pound sterling from the gold standard it became clear that it would require more time in office. Meanwhile, the Labour Party expelled all those who were supporting the government, and MacDonald's decision to lead a Conservative-dominated coalition instead of the party he had co-founded was labelled a "betrayal" by his erstwhile colleagues and supporters.

The Conservatives began pressing their partners to fight an election together as a combined unit in order to secure a mandate for radical economic reform, and MacDonald's supporters from the Labour Party formed the National Labour Organisation to support him. While initially against an early election, MacDonald came to endorse the idea in order to take advantage of Labour's unpopularity due to its poor economic record in office.

However, the Liberals were sceptical about an election and had to be persuaded. The key issue was the Conservatives' wish to introduce protectionist trade policies: the majority of the Liberals, led by Sir Herbert Samuel, were opposed, considering support for free trade to be a non-negotiable component of the Liberal political tradition. The argument split the party in half: Samuel withdrew the Liberals from the National Government (though continued to lend it their confidence, and still stood in the election as part of the coalition), while the National Liberals—under the leadership of Sir John Simon—remained, willing to support protectionism.