This book investigates the growing role of regional organizations in sustainable governance, emphasizing their reciprocal interactions with multilateral institutions like the United Nations. Focusing on the European Union as a key case study, it explores multilevel governance, policy coherence, and the implementation of sustainable development initiatives. With a mix of theoretical perspectives, real-world examples, and forward-looking analysis, this book serves as an essential resource for academics, policymakers, and practitioners interested in governance, sustainability, and regional integration.