This textbook provides a comprehensive introduction to the study of international diplomacy, covering both theory and practice. The third edition has been updated and revised, with new chapters on the digital turn, contemporary crises, and power shifts in modern diplomacy. By integrating historical traditions from Europe, China, and the Middle East with modern diplomatic challenges, this book: Traces the evolution of diplomacy from its historical foundations to its modern institutionalised form, examining how shifting power dynamics, technological revolutions, and geopolitical crises have shaped its trajectory Examines theoretical perspectives on diplomacy as a communicative practice, exploring how diplomats interpret and project power, negotiate international norms, and sustain diplomatic agency in an increasingly fragmented world order Analyses diplomacy in the digital age, investigating how new technologies, social media, and artificial intelligence reshape diplomatic interactions, redefine state and non-state engagement, and challenge traditional diplomatic norms in a rapidly evolving global information environment. This new edition offers an up-to-date, accessible, and authoritative overview of how diplomacy works and, indeed, ought to work in a globalised world. It will be essential reading for students of international diplomacy and is highly recommended for students of crisis negotiation, international organisations, foreign policy, and international relations.