Abstract: The subject of this research is the legal definition of the concept of “unfair competition” established by the Federal Law “On Protection of Competition”. The goal of this research is to analyze the content of this legal definition, determine its elements, as well as assess the legal definition from the perspective of its unambiguousness and correspondence to the goal of regulation of relations pertaining to protection from unfair competition, including through the analysis of the existing views within the doctrine. The novelty of this research consists in the critical analysis of the existing within legal science approaches towards assessment of legal definition of unfair competition formulated in Russian legislation, as well as postulation of a previously undiscussed problem pertaining to establishment of such sign of unfair competition as possibility of causing losses. The conclusion is made on correspondence of the legal definition of unfair competition in the current legislation to the goals of efficient protection of competition contrary to critical assessments that are prevalent within the doctrine, as well as on the necessity to form a uniform approach of the practice towards proving the possibility of inflicting losses as a sign of unfair competition.