In this article is highlighted the life and scientific milestones of the famous historian, corresponding member of the National Academy of Sciences of Ukraine, numismatist, medievalist, source historian, historiograph, author of more than a thousand scientific and popular science publications – Mykola Fedorovych Kotlyar. The formation of Mykola Kotlyar as a scientist was closely connected with numismatic studies, in the field of which he achieved considerable success. The researchers, who are dealing with the problems of Ukrainian numismatics, cannot pass over the scientist’s publications, that is why he became one of the most quoted Ukrainian numismatists, and over the years of fruitful work has gained recognition both in Ukraine and far beyond. As a student and delegate of the numismatic school of I. G. Spaskyi, M. Kotlyar inherited the research traditions of the Leningrad school, which he successfully implemented on the Ukrainian ground. Due to the fact that there had not been any qualified specialists, as well as systematic source base and appropriate methodology, the numismatic research in Ukraine had almost not been conducted before the beginning of Mykola Kotlyar’s active scientific career. In fact, starting from his scientific research it is possible to talk about the beginning of a new stage in the development of modern Ukrainian numismatics. The scientist was one of the initiators of the establishment of scientific publications in Ukraine, in particular, “Numismatics and Sphragistics” and “Historical Sources and Their Uses”, in which numismatists and specialists in other special historical disciplines were able to publish research results. Particular attention in the publication is focused on the achievements of the scientist, whose merit is the primacy in the complex study of the late medieval domestic issues, topography of numismatic finds, reconstruction of money circulation, money-weight and counting systems of medieval and early modern Ukraine. Mykola Kotlyar’s numismatic studies contributed to the formation of modern Ukrainian numismatics that studies a wide range of general historical problems. It basically turned it from a discipline that had not gone beyond external criticism of the source into a field of historical science. In his numismatic search the scientist used the latest modern techniques, and his understanding of the object of study was not limited to a coin or treasure, but included weights, stamps, written sources. Along with the emission and money circulation, the monetary metrology, money economy and the number of coins also became the subject of Mykola Kotlyar’s scientific studies. Such a complex approach, in which the coin was transformed from an independent object of study into a source, allowed M. Kotlyar to clarify a number of previously unknown or debatable socio-economic problems and processes. In particular, Mykola Kotlyar emphasized the regional types of money circulation in Kyivan Rus since the middle of the 8th century. According to the scientist “The Coinless period” is conventionally coinless for Southern Rus. Apart from that he proved that the emission of coins in Lviv and Kyiv in the late medieval period was a local Ukrainian phenomenon and in early modern times the money market of Ukraine was actively influenced by international trade and other factors. Monographs of the scientist “Galician Rus in the second half of the 14th – first quarter of the 15th century: historical and numismatic research” (1968), “Money circulation of Ukraine in the era of feudalism” (1971) and “Essays on the history of circulation and numbers of coins in Ukraine in the 14th – 18th century” (1981) immediately became a bibliographic rarity and provided M. Kotlyar with the status of an outstanding numismatist. To summarize, we can confidently state that the numismatic studies of Mykola Fedorovych Kotlyar opened new opportunities for historians and became the basis for the formation of modern Ukrainian numismatics.