This textbook explains the notion of monetary union, highlighting the key concepts, procedures, and challenges involved. The book is organized in three parts. In the first part, the reader learns about monetary issues, like definitions and typology of monetary unions, rationale of monetary unions, monetary policy, monetary institutional matters. The second part is devoted to fiscal matters and the interplay between fiscal and monetary policies, such as deficits, transfers, public debt sustainability issues, fiscal policy, policy mix. The last part focuses on other distinct but related issues, necessary to complete the union: banking and fiscal unions, structural adjustments in a monetary union. It ends with a chapter on the fate of monetary unions: how they develop, mature and sometimes dissolve.The book addresses students at undergraduate and graduate level, interested in a better understanding of international macroeconomics and monetary unions, as well as policy-makers, practitioners and economists in central banks, ministries of economics, economic institutions and banks.