The engagement of energy customers has been considered an important pillar of the European Union (EU) strategy to reach net-zero greenhouse gas emissions by 2050, while preserving a competitive and secure energy system. The legislative package Clean Energy for all Europeans (CEP), adopted by the EU in 2019, confirms the relevance of removing the existing barriers for end users not only to choose their energy supplier but also to invest in distributed generation and storage and participate in all energy markets. Interestingly, the new European legal framework goes beyond the recognition of the rights and duties of individual active customers, the so-called prosumers, and introduces for the first time an explicit reference to energy communities, which take two specific definitions: citizen energy communities (CECs) and renewable energy communities (RECs). This article provides the reader with an introduction to the concept of energy community and the reasons why European policymakers decided to foster the emergence of this type of actor in the energy system (the section “Collective Actors to Support the Energy Transition”). It then presents the main elements of the new European legal framework, highlighting both the similarities and the differences that exist between CECs and RECs (the section “The European Legal Framework”). After that, the article illustrates some of the critical issues that have emerged and the opportunity that the current energy crisis in Europe may represent (the section “Critical Issues and Future Opportunities”). Finally, a summary of the article is provided (the “Conclusions” section).