This book explores the world of regionalism and its evolution in many regions in the first quarter of the 21" century. With scholars focusing on the South Asian Association for Regional Cooperation (SAARC), the European Union (EU), the Shanghai Cooperation Organization (SCO), the Bay of Bengal Initiative for Multi-Sectoral Technical and Economic Cooperation (BIMSTEC), the Greater Mekong Subregion (GMS), as well as the impact of maritime security, nuclear weapons, economic challenges and legal frameworks, this book provides the researcher and enthusiast with an in depth review of regionalism.