How do non-state actors matter in international relations? This volume recognizes and examines three types of non-state actor: non-governmental organizations (NGOs), intergovernmental organizations (IGOs) and transnational corporations. It illustrates how they play roles alongside nation-states and are interrelated in matters of international regulation and coordination. Accessible and articulately written, this comprehensive collection of state-of-the-art essays is essential for both scholars and practitioners in international relations.