This book provides a comprehensive framework for understanding and measuring global justice across nations. By integrating theoretical foundations with empirical assessment, it offers a pioneering approach that bridges the gap between abstract philosophical concepts and practical evaluation methods. The first part establishes the conceptual foundations of global justice, exploring its theoretical underpinnings, key principles, and methodological challenges. The second part applies this framework to ten critical global issues: climate change, peacekeeping, humanitarian aid, anti-terrorism and conflict, cross-national criminal police cooperation, refugees, anti-poverty efforts, education, public health, and the protection of women and children. Through rigorous analysis of these domains, the book constructs a novel Global Justice Index that ranks countries based on their contributions to global justice. Intended for academics, policymakers, and students in international relations, political philosophy, and global governance, this volume combines theoretical depth with empirical rigor. It breaks new ground by moving beyond traditional state-centric approaches to international relations and offering instead a justice-centered perspective on global challenges. The book's most significant contribution lies in its systematic quantification of global justice, providing a tool for assessment and comparison that can inform policy decisions and international cooperation efforts.