This chapter examines the different regional arrangements that have emerged around the globe. It considers whether there has been a uniform process of regional cooperation and integration across all continents, the driving forces in the establishment of various forms of regional cooperation, and the extent to which cooperation at the regional level changes the nature of international politics. After clarifying the various concepts and definitions associated with regionalism, the chapter discusses relevant developments in the Americas, Africa, Asia, and Europe. In particular, it looks at regional arrangements in Eurasia and the post-Soviet states. It also explores the process of European integration as well as the similarities and the differences among the various regional arrangements, with particular emphasis on the unique circumstances that shaped the emergence of the European Union. There is an Opposing Opinions box that asks whether regional cooperation strengthens the state.