This introductory chapter presents the book’s central inquiry: how to understand that, through the establishment of the European Public Prosecutor’s Office (EPPO), the EU has acquired binding penal powers usually reserved for and jealously guarded by nation-states? The EPPO, introduced as a new EU actor aimed at protecting European public money, has significant implications for fundamental rights and freedoms and states’ monopolies on the legitimate use of force. The chapter highlights the challenging adoption process of the EPPO and outlines the core argument: that the EPPO is the result of the accommodation of conflicting norms and interests associated with supranational European integration, on the one hand, and national sovereignty, on the other hand, arbitrated in a complicated process of persuasion, bargaining, and institutional power games. This book aims to: (1) uncover the power relations influencing the creation of the EPPO; (2) examine the nature of conflicts during those negotiations; (3) demonstrate the transformative power of discourses by presenting perspectives of key actors on EU financial protection, national sovereignty, and supranational integration; and (4) ultimately, understand the establishment of a supranational criminal justice system via the EPPO.