This book analyses the principle of equality from three perspectives: public international law, private international law and EU law. It is the first book in English providing a comprehensive overview of this principle in these areas of law and showing the current trends and issues concerning its application. Its main goal is to understand whether and to what extent the principle of equality has been affirmed in public and private international law, as well as EU law, and what – if any – the common core of this principle is. The analysis carried out in this contributed volume starts from general analyses of the principle of equality in the areas of the law covered by the book and then discusses the principle in more specific areas, such as human rights law, international adjudication (including investment law) and the law of international organizations. The book is intended to become a benchmark for academics dealing with matters of equality in public international law, private international law and EU law. It will be a useful tool for practitioners too, the collected chapters being based on the relevant case law dealing with the principle of equality. Daniele Amoroso is Professor of International Law in the Department of Law of the University of Cagliari, Cagliari, Italy. Loris Marotti is Assistant Professor of International Law in the Department of Law at the Federico II University of Naples, Italy. Pierfrancesco Rossi is Postdoctoral Fellow in International Law in the Department of Law of Luiss University, Rome, Italy. Andrea Spagnolo is Professor of International Law in the Department of Law of the University of Turin, Turin, Italy. Giovanni Zarra is Professor of International Law and International Litigation in the Department of Law at the Federico II University of Naples, Italy.