The Labour Party is a centre-left political party and current ruling party in the United Kingdom. Founded at the start of the 20th century, it has been since the 1920s the principal party of the left in England, Scotland and Wales, but not Northern Ireland, where it has only recently organised again. Under New Labour, the party's position moved towards the centre.

Labour surpassed the Liberal Party as the main opposition to the Conservatives in the early 1920s. It has had several spells in government, first as minority governments under Ramsay MacDonald in 1924 and 1929-31, then as a junior partner in the wartime coalition from 1940-1945, and then as a majority government, under Clement Attlee in 1945-51 and under Harold Wilson in 1964-70. Labour was in government again in 1974-79, under Wilson and then James Callaghan, though with a precarious and declining majority.

The current national Labour government won a landslide 179-seat majority in the 1997 general election under the leadership of Tony Blair, its first general election victory since October 1974 and the first general election since 1970 in which it had exceeded 40% of the popular vote. The party's large majority in the House of Commons was slightly reduced to 167 in the 2001 general election and more substantially reduced to 66 in 2005. Labour is also the leading partner in the coalition Welsh Assembly Government, is the main opposition party in the Scottish Parliament, and has representation in the European Parliament. The current party leader is Gordon Brown.