The 2016 United Kingdom European Union membership referendum, commonly referred to as the EU referendum or the Brexit referendum, was a referendum that took place on 23 June 2016 in the United Kingdom (UK) and Gibraltar under the provisions of the European Union Referendum Act 2015 to ask the electorate whether the country should continue to remain a member of, or leave, the European Union (EU). The result was a vote in favour of leaving the EU, triggering calls to begin the process of the country's withdrawal from the EU commonly termed "Brexit".
Since 1973, the UK had been a member state of the EU and its predecessor the European Communities (principally the European Economic Community), along with other international bodies. The constitutional implications of membership for the UK became a topic of debate domestically particularly regarding sovereignty. A referendum on continued membership of the European Communities (EC) to try and settle the issue was held in 1975, with 67% of voters approving continued membership. Between 1975 and 2016 as European integration deepened, subsequent EC/EU treaties and agreements were ratified by the UK Parliament but without any public approval. Following the Conservative Party's victory at the 2015 general election as a main manifesto pledge, the legal basis for the EU referendum was established through the European Union Referendum Act 2015. Prime Minister David Cameron also oversaw a renegotiation of the terms of EU membership, intending to implement these changes in the event of a Remain result. The referendum was legally non-binding due to the ancient principle of parliamentary sovereignty, although the government promised to implement the result.
