Welsh Labour, formerly known as the Labour Party in Wales, is an autonomous section of the United Kingdom Labour Party in Wales and the largest party in modern Welsh politics. Welsh Labour and its forebears have won a plurality of the Welsh vote at every UK general election since 1922, every Assembly and Senedd election since 1999, and all elections to the European Parliament in the period 1979–2004 and in 2014. Welsh Labour holds 22 of the 40 Welsh seats in the UK Parliament, 30 of the 60 seats in the Welsh Senedd and 576 of the 1,264 councillors in principal local authorities including overall control of 10 of the 22 principal local authorities.

The Labour Party is a political party in the United Kingdom that has been described as an alliance of social democrats, democratic socialists, and trade unionists. The Labour Party sits on the centre-left of the political spectrum. In all general elections since 1922, Labour has been either the governing party or the Official Opposition. There have been six Labour prime ministers and thirteen Labour ministries. Since the 2010 general election, it has been the second-largest UK political party by the number of votes cast, behind the Conservative Party and ahead of the Liberal Democrats. The party holds the annual Labour Party Conference.