This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book examines the impact of the Brexit process internally on the polity, economy and society of the UK. Michael Keating's chapter assesses Scotland's position in the light of the Brexit vote against the backdrop of the 2014 referendum on Scottish independence and the ongoing political tensions between nationalism and unionism in Scotland. Leila Simona Talani's chapter considers the likely impact of Brexit on the City of London. Andrew Baker and Scott Lavery examine the political-economic implications of the Brexit decision. Jed Odermatt's contribution investigates the long-term consequences of the UK gaining considerable autonomy over trade policy in the aftermath of Brexit. Henrik Larsen examines the role of the European Union (EU) as an international actor in the wake of Brexit. The book addresses the potential impact of the Brexit vote on the institutions of the EU itself.