This chapter provides an overview of electoral systems and their implications for party systems and political representation from the perspective of the principal-agent framework adopted in this book. First, we present an overview of the variety of electoral systems in use in Europe. Even though most elections in Europe are held using proportional representation, there are important institutional differences. Second, we turn to direct demo- cratic elections and discuss the use of referendums and initiatives, specifcally with regard to questions about the European Union. We then move to the effects of electoral systems on the party system and discuss electoral system changes in Europe.