In the United Kingdom, devolution (historically called home rule) is the Parliament of the United Kingdom's statutory granting of a greater level of self-government to parts of the United Kingdom, such as to Scotland, Wales, Northern Ireland and parts of England, specifically to London and the combined authorities.

Statutory powers have been awarded to the Scottish Parliament, the Senedd (Welsh Parliament), and the Northern Ireland Assembly, with authority exercised by their associated executive bodies: the Scottish Government, Welsh Government, and Northern Ireland Executive respectively. In England, oversight powers and general responsibility have also been given to the London Assembly, which oversees the Greater London Authority and Mayor of London; and, since 2011, various mayoral combined authorities throughout England. There have been further proposals for devolution in England, including national devolution, regional devolution (such as to northern England or Cornwall) or failed proposals for regional assemblies.

Devolution differs from federalism in that the devolved powers of the subnational authority ultimately reside in central government, thus the state remains, de jure, a unitary state. Legislation creating devolved parliaments or assemblies can be repealed or amended by parliament in the same way as any statute, although the parliaments and assemblies in Scotland, Wales, Northern Ireland and London, as well as some mayors in England, were supported via public referendums. Laws such as the Scotland Act 2016 and Wales Act 2017 affirmed the permanence of their devolved institutions, and any abolishment of such must be voted for in a referendum.

Legislation passed following the EU membership referendum, including the United Kingdom Internal Market Act 2020, undermines and restricts the authority of the devolved legislatures in both Scotland and Wales.

Northern Ireland was the first constituent of the UK to have a devolved administration. Home Rule came into effect for Northern Ireland in 1921, under the Government of Ireland Act 1920 ("Fourth Home Rule Act"). The Parliament of Northern Ireland established under that act was prorogued (the session ended) on 30 March 1972 owing to the destabilisation of Northern Ireland upon the onset of the Troubles in late 1960s. This followed escalating violence by state and paramilitary organisations following the suppression of civil rights demands by Northern Ireland Catholics.

The Northern Ireland Parliament was abolished by the Northern Ireland Constitution Act 1973, which received royal assent on 19 July 1973. A Northern Ireland Assembly was elected on 28 June 1973 and following the Sunningdale Agreement, a power-sharing Northern Ireland Executive was formed on 1 January 1974. This collapsed on 28 May 1974, due to the Ulster Workers' Council strike.

The Northern Ireland Constitutional Convention (1975–1976) and second Northern Ireland Assembly (1982–1986) were unsuccessful at restoring devolution. In the absence of devolution and power-sharing, the UK Government and Irish Government formally agreed to co-operate on security, justice and political progress in the Anglo-Irish Agreement, signed on 15 November 1985. More progress was made after the ceasefires by the Provisional IRA in 1994 and 1997.

The 1998 Belfast Agreement (also known as the Good Friday Agreement), resulted in the creation of a new Northern Ireland Assembly, intended to bring together the two communities (nationalist and unionist) to govern Northern Ireland. Additionally, renewed devolution in Northern Ireland was conditional on co-operation between the newly established Northern Ireland Executive and the Government of Ireland through a new all-Ireland body, the North/South Ministerial Council. A British–Irish Council covering the whole British Isles and a British–Irish Intergovernmental Conference (between the British and Irish Governments) were also established.