This textbook provides not only a theoretical and conceptual orientation but also comparative insights into the different regional order models, norms, and institutions of Europe, Asia, Africa, and the Americas. In a second step, interregional relationships and cooperation are analyzed using selected case studies and policy areas. This introduction thus responds to the resurgence of the significance and study of regions and regionalism in international relations. In the context of centralization trends and globalization processes, regionalism is often seen as a countertrend in the form of decentralization and differentiation. However, regionalization processes represent an independent phenomenon in international politics, with their specific manifestations and functions varying from region to region.