1. Introduction

Referendums play an increasingly significant role in European politics at both national and European Union (EU) level. Whether it is joining the EU, amending the EU treaties or even leaving the EU, citizens have repeatedly been invited to give their views on European matters in a significant shift from representative democracy towards direct democracy. On other constitutional and social issues, as well as matters of foreign policy and ratification of international treaties, referendums have come to the fore in recent years, both within EU member states and would-be member states, and in non-EU European states, most notably Switzerland. This chapter introduces the themes discussed in this volume, including the rationale for holding referendums, the rules in place, how they play out in practice and whether the outcomes are respected, as well as looking at the relationship between referendums and representative democracy.