From trade relations to greenhouse gases, from shipwrecks to cybercrime, treaties structure the rights and obligations of states, international organizations, and individuals. For centuries, treaties have regulated relations among nation states. Today, they are the dominant source of international law. Thus, being adept with treaties and international agreements is an indispensable skill for anyone engaged in international relations. This revised and updated edition provides a comprehensive guide to treaties, shedding light on the rules and practices surrounding the making, interpretation, and operation of these instruments. The chapters are designed to introduce the law of treaties and offer practical insights into how treaties actually work. Foundational issues are covered, including what treaties are and when they should be used, alongside detailed analyses of treaty formation, application, interpretation, and exit. Special issues associated with treaties involving the European Union and other international organizations are also addressed. These are complimented by a set of model treaty clauses. Real examples illustrate the approaches that treaty-makers can take on topics such as entry into force, languages, reservations, and amendments. The book thus provides an authoritative reference point for anyone studying or involved in the creation or interpretation of treaties or other forms of international agreement.