The chapter analyses the three foundations of the new EU framework for macroeconomic governance, the European Macroeconomic Constitution. The provisions of the Maastricht Treaty stem from a rich background that informs about the content of the provisions and how they were assumed to lead to a successful monetary union. First, the economic constitutional thinking, originally by the German ordoliberal can be considered the philosophical foundation that informs how and why constitutional law addresses economic issues, particularly the monetary order. Second, longer evolution in central banking on one side and development in macroeconomic and monetary theory on the other side form the economic foundation. It informs about the assumption and content of various economic concepts and particularly about the 1990s broad consensus on central banking economics. Third, the institutional foundation is built on the institutional, legal and political development of the Community towards the establishment of the EMU. In the early 1990s, these three foundations happened to meet at the same intellectual crossroads that made EMU possible.