This book is a comprehensive overview of multiple nationality in international law, and contains a survey of current State practice covering over 75 countries. It examines the topic in light of the historical treatment of multiple nationality by States, international bodies and commentators, setting out the general trends in international law and relations that have influenced nationality. While the book's purpose is not to debate the merits of multiple nationality, but to present actual state practice, it does survey arguments for and against multiple nationality, and considers States' motivations in adopting a particular attitude toward the topic. As a reference work, the volume includes a detailed examination of the nature of nationality under international law and the concepts of nationality and citizenship under municipal law. The survey of State practice also constitutes a valuable resource for practitioners.