With the recent entry into force of the European Dispute Resolution Directive, the term international double taxation has gained legal relevance. This calls for revisiting the definition of international double taxation. This contribution presents the main approaches in the scholarly literature and demonstrates that the widely accepted definition of international double taxation is imprecise. Considering the function of tax treaties, it should instead be understood as a specific disadvantage to cross-border situations resulting from taxation by two or more states. Thus, neither discrimination by solely one state nor virtual double taxation constitute international double taxation in this context. The opposite is valid for intertemporal double taxation when new treaty rules must be created. The European Dispute Resolution Directive accords with the discrimination approach advocated here and substantiates the requirement of discrimination through three different variants.