The European Union (EU) faces many crises and risks to its security and existence. While few of them threaten the lives of EU citizens, they all create a sense of anxiety and insecurity about the future for many ordinary Europeans. This comprehensive volume explores the concept of 'ontological security' which was introduced into international relations over a decade ago to better understand the 'security of being' found in feelings of fear, anxiety, crisis, and threat to wellbeing. The authors make use of this concept to explore how narratives of European integration have been part of public discourses in the post-war period and how reconciliation dynamics, national biographical narratives and memory politics have been enacted to create ontological security. Within this context, they also discuss the anxiety of the 'remainers' in the Brexit referendum and the consequences of its failure to address the ontological anxieties and insecurities of remain voters. The book also explores: how European security firms market ontological security and provide an ontological security-inspired reading of the EU's relations with post-communist states; the EU and NATO's engagement with hybrid threats; and the EU as an anxious community. This book was originally published as a special issue of the journal European Security.