Building on the recent initiative to truly globalize the field of international relations, this book provides an innovative interrogation of regionalism. The book applies a globalizing framework to the study of regional worlds in order to move beyond the traditional conception of regionalism, which views regions as competing blocs dominated by great powers. Bringing together a wide range of case studies, the book shows that regions are instead dynamic configurations of social and political identities in which a variety of actors, including the less powerful, interact and partake in regionalization processes and have done so through the centuries.