Brexit is the exit of the United Kingdom from the European Union in the manner provided for in Article 50 of the Treaty on European Union, as a consequence of the referendum on the continued existence of the United Kingdom in the European Union, held on 23 June 2016, in which 51.89% of British voters voted to leave the Union while 48.11% voted to remain in the EU. The British government formally announced the country's withdrawal in March 2017, launching withdrawal negotiations. The release was initially delayed by the British parliament and by disagreement on some points in negotiations with the European Union.

Many effects of Brexit depend on how closely linked the UK will be to the EU or whether the transition period ends without a deal. Economists think that Brexit is likely to damage the UK economy and reduce its real per capita income in the long term and that the referendum itself has damaged the economy. Following Brexit, EU law and the Court of Justice of the EU no longer have supremacy over the laws of the United Kingdom or its Supreme Court, except on a temporary basis.