This chapter discusses the currency union’s original set-up. It first discusses the history of European monetary integration, distinguishing between two sorts of motives: one economic, the other political. From the establishment of the European Economic Community up until the Treaty of Maastricht, both have been important drivers of monetary integration. The chapter subsequently turns to the original legal set-up of the euro, in particular its internal policy dimension. The economic and political forces behind the currency union’s creation also exercised great influence on its set-up, which came to institutionalise a stability paradigm. Characteristic of this paradigm was that it granted overriding importance to price stability as a policy goal and argued for a privileged position of the central bank in achieving this. The chapter shows how its influence was most notably evident at the level of aims and principles and in the constitutional position of the European Central Bank. Yet it also shaped the single currency’s economic foundations, in particular, the Union’s limited competences in this area and its focus on fiscal prudence. It even informed the rules governing accession.