This chapter provides a general overview of the Handbook of Comparative Regionalism. First, it establishes that the Handbook constitutes a major stock-taking attempt promoting truly comparative approaches across and within regions. The volume goes beyond state-led regional institution-building to include bottom-up societal regionalization processes as well as informal institutions and practices. The Handbook also encourages scholars of comparative regionalism to “de-center” the European Union and to treat it as a particular regional order among many others. Second, the chapter introduces and defines key terms of the Handbook including region, regionalism, regionalization, regional order, and regional governance. The chapter also provides an overview of the structure of the Handbook, its various parts and chapters.