Abstract: This article explores the main approaches of Russian and foreign authors towards big data definition; reflects the classification of data, components of big data; and provides comparative characteristics to legal regulation of big data. The subject of this research is the legislation of the Russian Federation and legislation of the European Union that regulate the activity on collection, processing and use of big data, personal data and information; judicial and arbitration practice of the Russian Federation in the sphere of personal data; normative legal acts of the Russian Federation; governmental regulation of the Russian Federation and foreign countries in the area of processing, use and transmission of data; as well as legal doctrine in the field of research dedicated to the nature of big data. The relevance of this research is substantiated by the fact that there is yet no conceptual uniformity with regards to big data in the world; the essence and methods of regulating big data are not fully explored. The goal of this research is determine the legal qualification of the data that comprise big data. The task lies in giving definition to the term “big data”; demonstrate the approaches towards determination of legal nature of big data; conduct classification of big data; outline the criteria for distinguishing data that comprise the concept of big data; formulate the model for optimal regulation of relations in the process of activity on collection, processing, and use of the data. The original definition of big data in the narrow and broad sense is provided. As a result, the author distinguishes the types of data, reflects the legal qualification of data depending on the category of data contained therein: industrial data, user data, and personal data. Attention is also turned to the contractual form of big data circulation.