The thesis focused on the nationality of a company in the light of cross-border mobility and corporate liability. The concept of the nationality of a legal person directly defines the law applicable to it; often by two main principles, the incorporated seat and the real seat principles.The theory of incorporated seat determines the applicable company law by reference to the country in which the company is incorporated (registered).The theory of real seat determines the applicable company law by reference to the country in which the company has its actual real seat (head office/central administration). The subject is continually developing by the case law by the European Court of Justice, therefore some of the case law of the European Court of Justice regarding the nationality of a company is also presented in the thesis.