Following a 2016 referendum, the United Kingdom exited from the European Union at the end of January 2020. Since leaving the EU, numerous polling organisations have conducted surveys to gauge public opinion on rejoining the organisation. The trend of the poll data shows that, over time, support for Brexit has waned, while public opinion in the UK has gradually moved in favour of rejoining the EU (either totally, or partially, such as joining the European single market).^[1]

A referendum on the United Kingdom's membership of the European Union took place in 2016, following the European Union Referendum Act being approved by parliament the previous year.^[2][3] Most political parties, including Labour and the Liberal Democrats, supported remaining in the European Union while the governing Conservative Party remained neutral, with the prime minister, David Cameron, supporting the UK remaining in the European Union. A majority of voters supported the UK leaving the European Union, with 51.9% voting in favour of leaving and 48.1% in favour of remaining. Cameron resigned, and was succeeded by Theresa May and, later, Boris Johnson, both of whom negotiated the terms of the UK's departure. The UK's departure from the European Union led to two early general elections in 2017 and 2019, and dominated British politics until 31 January 2020, when the country's membership of the European Union ended.

In September 2023, thousands of people participated in a march in London campaigning for the United Kingdom to rejoin the EU.^[4] Also in September 2023, France and Germany proposed a restructuring of the membership of the EU to allow the UK to rejoin as an associate member, rather than a full member.^[5] Associate membership would include membership of the European single market but not the EU customs union, in exchange for participation in the European Court of Justice and making contributions to the EU budget.^[6] The president of the European Commission, Ursula von der Leyen, expressed her support for the UK eventually rejoining the EU.^[7] In September 2023 Keir Starmer, leader of the Labour Party, ruled out the possibility of the UK rejoining the EU under a Starmer-led Labour government.^[8]

Potential enlargement of the European Union is governed by Article 49 of the Maastricht Treaty. If the UK applied to rejoin the EU, it would need to apply and have its application terms supported unanimously by the EU member states.^[9] In January 2020, the political scientist Anthony Salamone wrote that member state support would seek "significant, stable and long-lasting majority public opinion in favour of rejoining", suggesting sustained 60% support would be a plausible minimum.^[9] New negotiated terms may also require the UK's participation in the Eurozone and Schengen Area, as well as offering fewer concessions than the UK received as a member.^[9] Any concessions sought when joining would need unanimous support from member states and a majority in the European Parliament.^[10]

Some UK political parties have policy proposals for the United Kingdom to rejoin the European Union in the future, while others have ruled out supporting it.^[11]

• Opinion polling on the United Kingdom's membership of the European Union (2016–2020)
• Accession of the United Kingdom to the European Communities
• Potential enlargement of the European Union
• United Kingdom membership of the European Union