This is a list of referendums related to the European Union, or referendums related to the European Communities, which were predecessors of the European Union. Since 1972, a total of 48 referendums have been held by EU member states, candidate states, and their territories, with several additional referendums held in countries outside the EU. The referendums have been held most commonly on the subject of whether to become a member of European Union as part of the accession process, although the EU does not require any candidate country to hold a referendum to approve membership or as part of treaty ratification. Other EU-related referendums have been held on the adoption of the euro and on participation in other EU-related policies. The United Kingdom is the only country as an EU member state to have held referendums on continued membership of the European Union and its antecedent organisation, the European Communities. In the first referendum in 1975, continued membership of what was then the European Communities (which included the European Economic Community, often referred to as the Common Market in the UK) was approved by 67.2% of voters, while in its second referendum in 2016 voters voted by 51.9% to leave the European Union, effectively reversing the result of the first referendum. Greenland, an autonomous territory of Denmark, voted to leave the EC in a referendum in 1982 by 53% of voters.

Summary of referendums on membership

EC enlargement of 1973

In 1972, four countries held referendums on the subject of the 1973 enlargement of the European Communities. Denmark, Ireland, and the United Kingdom were admitted as members of the EC, acceding on 1 January 1973.

United Kingdom's European Communities membership, 1975

Greenland's European Communities membership, 1982

Single European Act

Two referendums were held in EU countries to permit them to ratify the Single European Act.

Maastricht Treaty

EU enlargement of 1995

In 1994, four countries, and one dependency, held referendums on membership of the EU, resulting in the 1995 enlargement of the European Union. Austria, Sweden, and Finland were admitted as members of the EU, acceding on 1 January 1995.

Treaty of Amsterdam, 1998

Two countries held referendums on the ratification of the treaty of Amsterdam.

Treaty of Nice, 2001

EU enlargement of 2004

The 2004 enlargement of the European Union involved ten candidate states, eight from Central and Eastern Europe, and the Mediterranean islands of Malta and Cyprus. In 2003, referendums on joining the EU were held in all these nations except Cyprus. Since the results were in favourable in all cases, all ten candidate countries were admitted as members of the EU, acceding on 1 May 2004.

Euro

Denmark and the United Kingdom received opt-outs from the Maastricht Treaty and do not have to join the euro unless they choose to do so; Sweden has not received an opt-out, yet deliberately does not live up to the requirements for joining. Two referendums have been held on the issue, both of which rejected accession.

European Constitution, 2005

Several member states used or intended to use referendums to ratify the Treaty establishing a Constitution for Europe (TCE). Referendums were planned, but not held, in:

Treaty of Lisbon

Only one member state, Ireland, obliged by their constitution, decided on ratification of the Treaty of Lisbon through a referendum.

European Fiscal Compact, 2012

EU enlargement of 2013

Croatia was admitted as a member of the EU, acceding on 1 July 2013.

San Marino membership application

A referendum was held in San Marino on whether the country should submit an application to join the European Union as a full member state.

Unified Patent Court

The Unified Patent Court is a proposed court between several EU member states, that, inter alia, is to be constituted for litigation related to the European Union patent.

Greek bailout referendum, 2015

Danish EU opt-out referendum, 2015

Dutch Ukraine–European Union Association Agreement referendum, 2016

United Kingdom's European Union membership, 2016

Hungary migrant quota referendum, 2016

North Macedonia membership, 2018

Danish EU opt-out referendum, 2022

Poland migrant quota referendum, 2023

Moldova membership, 2024

Agreements between Switzerland and the EU

Future referendums

Countries which seek to join the European Union in the future may hold a referendum as part of the accession process. Iceland, which submitted an application for EU membership in 2009 but subsequently suspended negotiations after a change in government, has debated holding a referendum on resuming negotiations. In addition, Article 88-5 of the Constitution of France requires a referendum there to ratify any future accession treaty. Politicians in other existing member states have proposed referendums in their states, particularly with reference to the accession of Turkey. There has been proposals by eurosceptic parties and movements across the EU on holding referendums on withdrawing from the EU, since the United Kingdom voted in favour of withdrawing in a 2016 referendum.