Two fish are swimming in a pond. 'Do you know what?' the fish asks his friend. 'No, tell me.' 'I was talking to a frog the other day. And he told me that we are surrounded by water!' His friend looks at him with great scepticism: 'Water? Whats that? Show me some water!' International lawyers often find themselves focused on the practice of the law rather than the underlying theories. This book is an attempt to stir up 'the water' that international lawyers swim in. It analyses a range of theoretical approaches to international law and invites readers to engage with different ways of legal thinking in order to familiarize themselves with the water all around us, of which we hardly have any perception. The main aim of this book is to provide interested scholars, practitioners, and students of international law and other disciplines with an introduction to various international legal theories, their genealogies, and possible critiques. By providing an analytical approach to international legal theory, the book encourages readers to enhance their sensitivity to these different approaches and to consider how the presuppositions behind each theory affect analysis, research, and practice in international law. International Law Theories is intended to assist students, scholars, and practitioners in reflecting more generally about how knowledge is formed in the field.