Apart from sketching the background to the book Ecocide: Criminalising Serious Harm against the Environment and providing an overview of its chapters, this introductory chapter by the editors briefly reflects on the difficult and at times tautological question of what ecocide is. It does so by analysing the compatibility of this ‘novel’ legal concept with international criminal law (hereinafter: ICL), the subfield of public international law dealing with (including regulating accountability processes for individuals responsible for violations of) international crimes, namely war crimes, crimes against humanity, genocide, and the crime of aggression. Indeed, how does the criminalisation of serious harm against the environment fit within ICL broadly construed, including the Rome Statute, the founding document of ICL’s most prominent actor, the International Criminal Court (ICC)? To this end, the book’s chapters address key questions: what constitutes ecocide, how can it be prosecuted, where should it be prosecuted, and who are its perpetrators and victims? In this critical-theoretical introduction, which is informed by the chapters in this book, we submit that the crime of ecocide can be compatible with ICL. However, paradoxically, we should be vigilant to not both expect too much of a crime of ecocide due to the inherent limitations of ICL as a discipline and to not expect too little either, since the crime could potentially capture a wide range of behaviour that could be considered part and parcel of everyday life, such as corporate activity.