The determination of nationality of corporations is one of the most challenging issues in the law of corporations. This challenge, which has emerged in two dimensions of the basis of nationality and the criteria for determining nationality, today is more focused on the second dimension, and the criteria of determining nationality still varies from one legal system to another. In Iranian law, this variation has also penetrated the scolars theories and some different theories have been presented regarding the criteria for determining nationality.
These raise three questions: First, what is the basis of the nationality of corporations; Second, what are the criterias for determining nationality and which are accepted by Iranian and EU law; Third, What role does registration play in granting the nationality of corporations in the recent jurisprudence of the European Court of Justice, and to what extent is this role compatible with the current Iranian legal system?
This research, in the framework of a descriptive-analytical method and based on comparative studies, has concluded that granting the nationality to the corporations is based on the identification of applicable law and the principle of diplomatic protection of corporations. In order to determine the concept, a various criterias are involved, such as theories of Lex incorporationis, Real seat, Control and Connecting Factor. The attitude of Iranian and EU law in identifying the single criterion are not explicit, but the new approach by ECJ has moved towards identifying the theory of Lex incorporationis. In Iranian law, the same theory is applicable in the provided interpretations of the law and jurisprudence.