Introduction. According to the population census in Russia in 2020-2021, in comparison with the 2010 census, the number of Mari people has significantly decreased (547605 → 423803), the number of Mari speaking their native language has decreased (451033 → 258722), the percentage of indigenous people in the population of the Republic of Mari El has decreased (41.7% → 36.4%). The presence of the Meadow Mari and the Hill Mari state languages for one people negatively affects the language situation in the republic. The traditional allocation of four dialects (Hill, North-Western, Meadow, Eastern) does not correspond to the new linguistic reality: The purpose of the study: based on the analysis of scientific publications on the system of dialects of the Mari language and based on the new linguistic situation in the Republic of Mari El, to propose a new classification of dialects of the Mari language based on the history of their formation, study and division. Materials and methods: statistical data of the population census in Russia in 2020-2021, scientific publications on the problems of dialectology of Finno-Ugric languages, considered on the basis of analysis, classification and logical comparison method. Research results, discussions. The formation of Mari dialects and their classification have a long history. In the XIX century, the Hill, Meadow and Eastern dialects of the Mari language were known. At the end of the XX century, they started talking about the North-Western dialect connecting the Hill and Meadow dialects. The Eastern dialect is close to the Meadow dialect in its linguistic indicators. Recent studies allow us to isolate two major dialects: Western and Eastern, which completely cover the area of the Mari language. Conclusion. G. Bereczki’s classification of dialects of the Mari language, which we qualified as the most suitable for systematizing the language, is built on the basis of a deep and comprehensive study of dialect material. It adequately reflects the current state of the Mari language, allows one to erase the boundaries between the Hill and Meadow dialects, contributes to the preservation of a single Mari language for the Mari people.