The (positive) competence-competence principle is one of the most fundamental principles of international arbitration. It provides the arbitral tribunal with the competence to decide on its own competence. These positive effects relating to the jurisdiction and the competence of the arbitral tribunal are nearly universally recognized, contrary to the consequences following from it for the jurisdiction of the state courts. Despite the positive effect’s broad recognition, its justification raises difficult questions which touch the very basics of arbitration. The entry discusses the historic and conceptual background of the principle as well as some of the controversial questions as to its scope and the form, timing and requirements of an arbitral tribunal’s jurisdictional decision, setting out the approaches adopted in the various jurisdictions.