Ireland–United Kingdom relations

Ireland–United Kingdom relations are the international relations between the Republic of Ireland and the United Kingdom of Great Britain and Northern Ireland. British rule in Ireland dates back to the Anglo-Norman invasion on behalf of the English king in the 12th century. Most of Ireland gained independence from the United Kingdom following the Anglo-Irish War in the early 20th century.

Historically, relations between the two states have been influenced heavily by issues arising from the partition of Ireland and the terms of Ireland's secession, its constitutional relationship with and obligations to the UK after independence, and the outbreak of political violence in Northern Ireland. Additionally, the high level of trade between the two states, their proximate geographic location, their common status as islands in the European Union until Britain's departure, common language and close cultural and personal links mean political developments in both states often closely follow each other.

Irish and British citizens are accorded equivalent reciprocal rights and entitlements (with a small number of minor exceptions), and a Common Travel Area exists between Ireland, the United Kingdom, and the Crown Dependencies. The British–Irish Intergovernmental Conference acts as an official forum for co-operation between the Government of Ireland and the Government of the United Kingdom on matters of mutual interest generally, and with respect to Northern Ireland in particular. Two other bodies, the British–Irish Council and the British–Irish Parliamentary Assembly act as a forum for discussion between the executives and assemblies, respectively, of the region, including the devolved nations and regions in the UK and the three Crown dependencies. Co-operation between Northern Ireland and Ireland, including the execution of common policies in certain areas, occurs through the North/South Ministerial Council. In 2014, the UK Prime Minister David Cameron, and the Irish Taoiseach Enda Kenny described the relationship between the two countries as being at 'an all time high'.

Both Ireland and the United Kingdom joined the European Union (then the European Communities) in 1973. However, the three Crown dependencies remained outside of the EU. In June 2016, the UK held a referendum in which a majority voted to leave the EU. Brexit became effective on 31 January 2020, with a deal being reached on 24 December, keeping Northern Ireland in the European Union Single Market for goods and keeping a free border between the Republic of Ireland and Northern Ireland. Relations between both sides became strained after the requested implementation of the Northern Ireland Protocol on 1 January 2021, which is strongly opposed by British citizens in Northern Ireland, the EU and the Irish government. Many Irish citizens in Northern Ireland saw Britain's withdrawal from the EU as a threat to the peace process and cross-border relations, especially as a majority of the NI electorate voted to remain in the EU. As a result of the tensions over the protocol, in February 2022, the DUP collapsed the Northern Ireland Assembly and Executive in protest, seeking a renegotiation of the deal. Consequently, Northern Ireland was left without a devolved executive government until February 2024, when the DUP re-entered following modifications to the protocol. This allowed a new NI Executive to be elected, with Michelle O'Neill of Sinn Fein becoming First Minister, alongside Emma Little-Pengelly of the DUP as deputy First Minister.

The three devolved administrations of the United Kingdom in Scotland, Wales and Northern Ireland, and the three dependencies of the British Crown, the Isle of Man, Jersey and Guernsey, also participate in multilateral bodies created between the two states, such as the British Irish Council and the British-Irish Parliamentary Assembly.