International courts and tribunals hold the power to decide on questions involving sovereignty over territory, grave human rights violations, international crimes, or millions of euros' worth of economic interests. Judges and arbitrators are the 'faces' and arguably the drivers of international adjudication. Yet certain groups tend to be overrepresented on international benches, while others remain underrepresented. Although international courts and tribunals differ in their institutional make-up and functions, they all rely in essence on the judgement of a group of individuals, each with their own background and experience. Even if adjudicators' identity is not the only, and may not be the decisive, influence on their decision-making, the relative lack of diversity has an effect on the judicial process and its outcomes, which in turn entails broader implications for the legitimacy of international law. This book analyses the implications of identity and diversity across numerous international adjudicatory bodies, focusing on a wide range of factors. Lack of diversity within the judiciary has been identified as a legitimacy concern in domestic settings, and the last few years have seen increasing attention to this question at the international level as well, making the book both timely and topical.