This paper presents an overview of recent ECJ case law concerning res judicata, with a focus on the way in which EU law affects national rules related to this principle. A series of recent judgments has confirmed the importance of the issue in the broader context of the impact of EU law on national judicial systems and the circulation of judgments. The ECJ mostly confirms trends visible in earlier case law, signalling an awareness of the importance of this rule for national judicial systems and restricting exceptions to what appears strictly necessary in order to ensure the effectiveness of EU law. However, the case law also presents interesting new developments, including a challenge of cross-jurisdictional national res judicata whose consequences are as yet unclear and a more in-depth engagement with national procedural systems on the basis of the principles of equivalence and effectiveness. The overall impression is one of maturation of the case law although some progress still needs to be made, in particular with regard to the clarity of the Court's discourse on EU and national principles of res judicata.