The article attempts to study the political and legal essence (nature) of international crime as a negative phenomenon of social reality within the analysis of various scientific approaches. The complex use of four scientific research methods (analysis, synthesis, formal legal, and comparative methods) allowed us to analyze different theoretical approaches regarding the concept definition of "international crime." The authors concluded that the concept "international crime" could be considered in four aspects in the modern doctrine of international criminal law: 1) acts that are expressed in state violation of international obligations arising from the operation of international norms of jus cogens, which predetermine the international legal responsibility; 2) acts that are expressed in state violation of international obligations arising from the operation of international norms of jus cogens, which entail the implementation of international criminal liability of individuals responsible for their commission; 3) acts that, due to specific forms of external expression, embody the highest character of public danger, allows us to characterize them as evil in itself (malum in se); 4) acts that infringe on definite elements of the international legal order -international peace and security of humanity. The definition of international crime is given, which means a complex act committed in the context of an institutionalized policy that encroaches on the international peace and security of humanity and causes concern to the international community and, as a result, falls under universal jurisdiction.