This book reflects on the reasons for the decline of international cooperation in world politics and studies ways to restore legitimacy in the international order. It engages with the concept of legitimacy in international relations theories and practices to examine the discussions around power shifts, the decline of liberalism, demands for inclusive international architectures, and challenges to multilateralism, as well as established norms by leaders and nationalisms. It studies the impact of the post-COVID-19 world order on the nature of power in the international system and changes in normative concerns of security. The volume also interrogates political legitimacy through an area studies lens by examining the concept of legitimacy separately in the USA, Europe, South Asia, Southeast Asia, Latin America, and Africa.An important and timely text featuring contributions from eminent scholars, this book will be of use to students and researchers of modern history, political science, and international relations. It will also be of interest to think tanks and policy-making bodies concerned with international affairs and foreign policy.