The article analyzes the concept of a transnational crime as a category of international criminal law, its concept and characteristic properties. The origins of the concept of “transnational crime” are considered, taking into account the diversity of sources of international law, conceptual approaches, the relation between concepts “transnational” and “transboundary”, as well as the features of the concept of transnationality are identified. Different approaches to this problem at the present stage of development of international criminal law are generalized. The author emphasizes the importance of the UN Convention against Transnational Organized Crime of November 15, 2000, which describes the transnationality, the criminalization of criminal acts (money laundering, corruption, etc.); measures to be taken to combat these crimes are determined; issues of jurisdiction, confiscation, arrest, extradition, protection of witnesses, international cooperation of states in the field of mutual legal assistance in the investigation, prosecution and trial of transnational crimes are regulated. It is emphasized that the concept of a transnational crime is based on such important precepts: transnationality; recognition of the crime of a transnational criminal act in the sources of international law and national legislation; national character of a criminal law ban; criminal liability for transnational crime should be based on the principle of legality; a great public danger of a crime, because such an act is detrimental not only to the direct object of the crime, but also to interstate relations.