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.
Before allowing the four new candidate member states to join the European Communities, founding member France held a referendum that approved this. Following the French approval, three of the four candidate states (Ireland, Denmark and Norway) likewise held referendums on the issue of joining the European Communities. The United Kingdom did not hold a referendum before joining.
In 1973, Greenland joined the European communities as part of Denmark. However, after the establishment of home-rule and eurosceptic Siumut winning the 1979 Greenlandic parliamentary election, a referendum on membership was agreed upon, in which the voters rejected remaining part of the communities. This resulted in Greenland negotiating the terms of its separation from the EU, resulting in the Greenland Treaty, and Greenland's leaving the communities in 1985.
Before the negotiations on the treaty of Maastricht began, Italy held a consultative referendum to give the European Parliament a popular mandate to elaborate a future European Constitution. After the treaty was signed, three countries held referendums on its ratification.
After the defeat of the treaty in the first referendum, Denmark negotiated and received four opt-outs from portions of the treaty: Economic and Monetary Union, Union Citizenship, Justice and Home Affairs, and Common Defence. The second referendum approved the treaty amended with the opt-outs.
In the so-called "Nice II referendum" in 2002, statements on Ireland not having to join a common defence policy and affirming the right to decide on enhanced cooperation in the national parliament were stressed in a special document, resulting in a favourable vote.
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.
After the first vote by Ireland on the Lisbon Treaty, the European Council and the Irish Government released separate documents, referred to as the "Irish Guarantees", that stated the other member countries would not use the possibility in the Treaty to diminish the number of permanent commissioners in favour of a rotating system with fewer commissioners, and not threaten Ireland's military neutrality and rules on abortion. With these assurances, the Irish approved the unchanged Lisbon Treaty in a second referendum.
A referendum on the bailout conditions in the Greek government-debt crisis. A majority of the voters rejected the bailout conditions. However, shortly afterwards the government accepted a bailout with even harsher conditions than the ones rejected by the voters.
The referendum was held to decide on converting the opt-out from participation in the area of Justice and Home Affairs area into an opt-in: the possibility for the Danes to decide on a case-by-case basis. The voters rejected the proposal.
Dutch Ukraine–European Union Association Agreement referendum, 2016