The article deals with the issue of the essence and signs of public interest. Public interest refers to the type of concepts with a variable component, regarding which there is no single approach in Russian theoretical and legal science. As the author notes, French scholars hold different views on the ratio of private interest to public interest, however, they recognize that there is necessarily a defense of both public interest and social and private interests in judicial practice. In Russia, the views of the legal school of the Soviet period traditionally dominated, uniting the public interest and the state itself. At the same time, there is no fixed concept of public interest in the normative acts. However, in recent years, approaches to the study of this legal concept have become much more complicated. According to some authors, public interest under certain conditions can be considered not within the framework of the philosophy of law, but legal sociology. The author identifies two main schools of political and legal doctrines that considered public interest as a separate category, traces the origins of the formation of the concept of public interest, starting from the views of Thomas Aquinas. The author pays attention to the need to define public interest carefully and delicately, since subjective circumstances can change the public interest essence. Finally, the author concludes that at present the public interest can be defined as a tool that contributes to the improvement of legal proceedings. The author recommends improving of procedural technique, as well as ensuring both the rights’ protection of individual members of society and the public interest.