This chapter is devoted to a historical overview of the concept of EU citizenship. Although formally introduced only in the 1992 Maastricht Treaty that established the modern-day European Union, the idea of Union citizenship appeared a long time before and developed over the course of decades. This chapter looks into the history of EU citizenship that goes back to the earliest stages of the European integration process and also pays attention to the developments that happened after the Maastricht Treaty. This historical study provides some background that is helpful for this book’s analysis of the contemporary development of Union citizenship in the wider context of EU law.