Introduction. Article 2 of the Convention on the Rights and Duties of States, on December 26, 1933, established the legal status of federal states in international relations, constituting a sole entity in the eyes of international law. It is an irrefutable fact that federations have always been a specific subject of international relations, due to their state structure. Simultaneously, despite the pervasive prevalence of the federal form of state structure in the modern world and the active involvement of numerous leading federal states in international relations, the meaning of the term “exclusivity of federal states” remains ambiguous. However, the peculiarities of the legal nature and state-territorial structure of federations, which impact both the internal structure of the system of power and governance and their external relations, highlight the significance of this theme. The present article examines a theoretical analysis of the concept of “exclusivity of federal states”. The study is based on a range of sources, including the constitutional acts of federal states, international treaties, and the research of domestic experts on various aspects of the theory and practice of federalism. In preparing this work, the author also used the findings of his own analysis of federal states. Methods. In analysing the concept of “exclusivity” in the context of federal states, the author viewed a federation as a special form of governance structure and state power. This implies that the constituent entities within the federation possess public legal status, which entails a dual-tier power structure of state and federal relations. The manner in which this public principle is expressed within the legal framework of the federation’s territorial structure constitutes the core content of the concept of “the exclusivity of federal states”. The methodological basis of the study encompassed formal-legal, comparative-legal, historical methods, and a systemic-structural approach. Results. The exclusivity of federal states is characterised by a legal feature, which is associated with the specifics of their internal state structure. This structure is based on the public regional principle (the internal public status of the constituent entities of federation). The concept “exclusivity of federal states” manifests in various forms of external representation, which can be categorized into three key conditions: the participation of the federation (or federations) in international relations, the transformation of the state-territorial structure of federal states, and the establishment of international or integration alliances and organisations. Simultaneously, in all forms of external representation of federal exclusivity, the legal status of the constituent entities of federation (regions) plays a pivotal role. The analysis of the legal exclusivity of federations also revealed additional nuances of “supranationality” concept, which in this context are linked to the concept of statehood.