The international community supports the idea of prosecuting those responsible for the crime of aggression. However, the participants in the ongoing war in Ukraine are not signatories to the Rome Statute of the International Criminal Court, and therefore, discussions continue on the possibility of prosecuting those involved in Russian aggression in the newly created special hybrid tribunal. The purpose of this study was to investigate, through legal analysis of international legislation and criminal legislation of Ukraine, the legal regulation of responsibility for the preparation, planning, unleashing, and waging of aggressive war. In the course of the study, the following scientific methods were used: formal-logical, logical-semantic, hermeneutical, statistical, comparative-legal. The study examines the norms of international criminal law and national legislation of Ukraine, which establish criminal liability for the crime of aggression and court sentences issued in Ukraine in this category of cases. The signs of the subject of the crime of aggression are analysed, and the question of which persons are subject to criminal liability for such acts is resolved. It was established that international criminal law and Ukrainian criminal law define the characteristics of persons who can be criminally responsible for unleashing and waging a war of aggression differently, as well as their planning and preparation. It was proved that the absence in the Criminal Code of Ukraine of a clear and literal indication of who can be considered the subject of the crime of aggression does not indicate that it can be any sane person of sixteen years of age. It was proved that this crime can only be committed by persons who are responsible for certain functions in the structure of the armed forces of the country or state power while making decisions in the field of military planning and management, directing, and exercising control over the military or political actions of the state that committed the act of aggression. Therefore, it was generalised that the qualification under Article 437 of the Criminal Code of Ukraine of actions of “ordinary” participants in military operations is erroneous. The results of the study can be used by investigators, prosecutors, judges in the criminal law qualification of the actions of accused or defendants; research and teaching staff and applicants for higher education in the study of criminal law disciplines; and for further scientific research