The European Citizens’ Panels (ECP), set up in 2021-2022 in the framework of the Conference on the Future of Europe (CoFoE), were presented by the European institutions as an “unprecedented project”. However, a call for a “direct participation of citizens” in European integration was already made by the Italian federalist Altiero Spinelli in the 1940s. At the end of the 1950s, Spinelli concretised this project by organising the very first experiment in participatory democracy on a post-national scale: the ‘Congrès du peuple européen’. Why has such a pioneering experiment been almost forgotten to this day, and what can it tell us about the current challenges of European participatory democracy? By crossing political history studies on European integration and deliberative studies on democratic innovations my research project intends to give historical depth to the current debates on the challenges, issues and limits of participatory democracy experimented at the post-national level of the EU.