Extended beyond the previous chapter’s analysis of the main problems raised by parallel proceedings, this chapter proposes a first way in which such risks can be reduced or eliminated altogether: a broader application of international res judicata. This chapter starts by defining and explaining the concept of international res judicata by comparing it to the understanding of the same concept in both civil law and common law jurisdictions. It then proceeds to argue for a broader and realistic (i.e., more flexible) application of this principle, which should be qualified as a principle of customary international law. This chapter also briefly addresses the principles of estoppel and lis pendens in international law and explains why they can be useful to answer the risks associated with parallel proceedings in the context of shareholders’ claims for reflective loss.