This chapter addresses the challenges to liberal democracy in Europe and how a questioned liberal democracy has become a threat to the European Union (EU) and European integration. This chapter reviews the research on democratization and autocratization and explores the democracy status among EU member states. It further discusses how previous decades of democratization provided for EU enlargements and an expanded democratic peace order, but how recent years of democratic decline has become an existential threat to the EU. The chapter concludes with a discussion of what the EU should do if some member states further declines into populism, illiberalism and autocracy.