This edited volume explores the obstacles to and opportunities for the development and entrenchment of a sustainable and representative multinational federalism. In doing so, it tackles a striking puzzle: on the one hand, scholars agree that deeply diverse multinational and multiethnic democracies should adopt federal structures that reflect and empower territorially concentrated diversity. On the other hand, there are very few, if any, real examples of enshrined and fully operative substantive multinational federalism. What are the main roadblocks to the adoption of multinational federalism? Can they be overcome? Is there a roadmap to realizing multinational federalism in the twenty-first century? In addressing these questions, this book brings together scholars from across the globe who explore a diverse range of cases from different and innovative analytical approaches. The chapters contribute to answering the above questions, each in their own way, while also addressing other important aspects of multinational federalism. The book concludes that the way forward likely depends on the emergence of a specific set of norms and a receptiveness to the complex institutional design.