Problem setting. As globalization processes deepen, the state’s position on the world stage increasingly begins to be determined by its overall competitiveness, which, in turn, directly depends on the structure and efficiency of the country’s innovation system. It is the innovative system that allows the state to occupy a certain niche in the system of international division of labor, to gain weight and status in the system of international relations. The problem of increasing international competitiveness is acutely facing Ukraine. It is not by chance that the question of the prospects for the formation of a national innovation system occupies a prominent place in the economic policy of Ukraine. Analysis of recent research and publications. The study of the concept, structure and subjects of the national innovation system is devoted to the work of various authors, in particular: Yu.E. Atamanova , K. Freeman , R. Nelson, B.A. Lundvall , L.I. Fedulova, A.A. Marakhovsky , M. Т. Sharko and others. However, the majority of research is purely economic in nature and is not closely «linked» to current national and foreign legislation. Target of the research is to study the concept and structure of the national innovation system, taking into account the analysis of the main economic-theoretical and legal approaches to the definition of this concept contained in the scientific literature and current legislation. Article’s main body. The article analyzes the main approaches to defining the concept of the national innovation system. It was found that most of these approaches are purely economic in nature, which complicates their use in the current legislation. It was established that in economic theory, the national innovation system is considered in three main aspects: 1) as a set of institutions whose activities are aimed at generating and spreading innovations; 2) as a complex of related economic mechanisms and types of activities that ensure innovative processes; 3) as part of the national economic system, which ensures the organic integration of innovative processes into the progressive development of the economy and society. The article also analyzes the definition of the concept of the national innovation system, which is contained in international legal acts and the legislation of Ukraine. The analysis of the definition of the concept of the national innovation system, which is proposed in the draft Innovation Code of Ukraine, was carried out. Based on the study of the concept and structure of the national innovation system, its main features were determined, namely. The national innovation system covers a complex of economically, organizationally and legally interacting subjects, which include: subjects of scientific, scientific and technical, innovative activity, innovative infrastructure, specially authorized bodies of state power and local self-government in the field of innovative activity; the focus of the subjects of the national innovation system on direct participation, provision or stimulation of innovations. The activities of the subjects of the national innovation system are aimed at carrying out scientific research and development with the aim of their further application in various sectors of the economy (in particular, the real sector) and the social sphere. On the basis of the research, a proper definition of the concept of the national innovation system was formulated as an ordered set of interrelated subjects of scientific, scientific and technical, innovative activity, innovative infrastructure, as well as state and local self-government bodies that develop, provide and support innovations. Considerable attention is paid to the study of the structure of the national innovation system. Despite the variety of available approaches to determining the structure of the national innovation system, special attention is paid to the study of the structure of the national innovation system. The main elements of the structure of the national innovation system are defined, which include state regulation, education, knowledge generation, innovation infrastructure and production. Conclusions and prospects for the development. Scientific literature and legislation contain different approaches to defining the concept and structure of the national innovation system. Among the variety of available approaches, the most justified is the institutional approach, the essence of which is to identify the national innovation system with a set of institutions (organizations, structures) that directly or indirectly participate in the process of ensuring or implementing innovative activities. In the legal sense, the national innovation system should be understood as an ordered set of interrelated subjects of scientific, scientific and technical, innovative activity, innovative infrastructure, as well as state and local self-government bodies that carry out the development, provision and support of innovative activities.