The concept of ‘security governance’ (SG) has increasingly gained currency in academic literature. In its initial appearances at the beginning of the 21st Century, the concept drew a sharp contrast with existing theoretical and analytical approaches, especially against the emergence of the mutated state system in Europe. The most recent understandings of the term, and those we deem more useful both from the theoretical and empirical points of view, underline the dual character of international politics, displaying both new and traditional features. In particular, the term becomes especially relevant to studies, including this book, that aim to understand and assess the European Union (EU)’s role in multilateral frameworks of cooperation. Thus, we endorse ‘multilateral security governance’ (MSG) as a conceptual framework for understanding complex forms of regulation and coordination among different actors at different levels.