This book examines the theoretical, historical, and practical dimensions of how a city operates internationally. It explores the various approaches of the contentious term "city diplomacy", its impact and follows examples throughout history, the origins of city diplomacy, and its evolution through traditional town-twinning, city networks, and smart cities. Cities have become important actors on the world stage, they have developed diplomatic apparatus and play an important role in securing sustainable futures across a range of key global issues, including climate change, inclusive economic growth, poverty eradication, housing, infrastructure, basic services, productive employment, food security, and public health. Practitioners along with scholars and students of political science, spatial planning, economic geography, international relations, and local government will find this an insightful, invaluable view of the subject.