The British referendum on continuing membership of the European Union (EU) in June 2016 represented a turning point in the relationship between the United Kingdom (UK) and the EU. This book investigates the implications of Brexit for the EU and the UK, placing this assessment in the context of the long-term evolution of UK-EU relations. The authors relate these findings to debates within the literature on EU policy-making, comparative politics, and political economy.The first part of this comprehensive volume explores the implications of Brexit for key policy areas, namely the single market, finance, and migration. The policies selected are those in which the consequences of Brexit are likely to be most significant because they are linked to the ‘four freedoms’ in the Single Market. The second part of the book explores important ‘horizontal’ or thematic issues, namely lessons from Brexit for theories of integration, the balance of power in the EU amongst the main member states post-Brexit, the evolution of the domestic political contestation in the EU, and the impact of Brexit on domestic politics in the UK. This book was originally published as a special issue of the Journal of European Public Policy.