The issue of consent to international law obligations and liabilities remains both highly complex in theory and extremely relevant in practice. Although the topic has been addressed quite regularly in the form of articles and chapters, there have been, surprisingly for such a central topic, few monographs on consent to international law in general and no edited volume in English language. Re-examining the issue of consent to international law in depth and in the contemporary circumstances of international law is a timely project therefore. The best way to do so in a rich and nuanced way is to give a voice to many authors at the same time, and this is the purpose of this collection of essays. This introduction sets the volume’s stage: first, it clarifies the relevance of the issue and the reasons that led to putting the book together; second, it introduces the main conceptual and normative challenges addressed in the volume and explains what it hopes to achieve; third, it provides some information about how the book is structured; and, finally, it sketches out the content of its successive chapters and their articulation.