In the doctrine, there are a variety of approaches to understanding the principles of international law, their role in regulating interstate relations. The study of principles in international law for the most part comes down to the consideration of its basic principles that form the basis of the international legal order. At the same time, the principles of international law are a multifaceted phenomenon and include their most diverse types. Revealing the legal nature of the principles of international law, revealing their essence and versatility is both theoretical and applied. The work is devoted to the study of the principles of international law as a social and legal phenomenon. Despite their fundamental, stable nature, the possibility of their evolution is shown. A classification of the principles of international law is presented, which makes it possible to more fully reveal their various essential aspects and specific features. On the basis of the dialectical approach, as well as the use of general research methods, the content of various types of principles of international law is presented. Their role in the regulation of interstate relations, law enforcement practice is shown. Much attention is paid to the study of the normativity of the principles of international law, their various types. The legal nature of the principles of international law, which have written and unwritten forms of their existence and expression, is considered. The complexity of deducing the unwritten principles of international law is shown. The interrelation of the principles reflected in various sources of international law is presented: international customs, international treaties, as well as those presented in the general principles of law. It was shown that the principles of international law: are an important legal category, a complex and multifaceted social and legal phenomenon, the basic regulator of interstate relations; contain the main ideas and approaches that reflect the state and needs of the development of interstate relations, the vital interests of the world community, its moral and political attitudes; had a decisive influence on the development of international law itself; predetermine the structure of interstate relations, their consistency and stability. It is especially emphasized that without them the functioning of international law, as well as adequate law enforcement and law-making activities, is impossible.