This book covers the relationship between the jurisdictional immunities of States and international organizations, addressing their similarities and dissimilarities. Their relationship with diplomatic immunity is also examined. It considers that the immunity of international organizations was historically conceived in terms of State immunity. The major aim of this book is to clarify the conceptual confusion that has often marred the understanding of the law of the, different but interrelated, jurisdictional immunities of both States and international organizations. The approach is to holistically analyze and synthesize select and relevant opinions of international and national courts.