This book provides the first comprehensive treatment of the principles shaping EU law: autonomy, conferral, equality, national identity, loyalty, solidarity, supremacy and effectiveness. Much has been written about principles of EU law inspired by national law, such as fundamental rights, but what of the principles that are specific to EU law? The book discusses the origins of the EU's structural principles, where they are located, and how they are applied in practice. The author proposes that these principles are deeply interrelated and ensure the legal unity and uniformity of EU law. Their role in the EU's external relations is also explored. This book brings a much-needed focus to the network of structural principles upholding the EU's constitutional order.