The work is devoted to the study of the legal concept of a financial service. The definition of the concept of a financial service is proposed and its content is established. The criteria for classifying financial services for the purposes of legal regulation are defined. As a result of the study, the author concludes that in the context of active changes in the financial services sector, it is advisable to adopt the broadest definition of the concept of financial services, as well as to systematically develop legal regulation of financial services in accordance with their classification based on the proposed criteria.