The purpose of the article is to highlight the contribution of the Czech historian and ethnologist Professor Jan Rychlík to the study of the history of Central and Eastern Europe. The research methodology was aimed at the analysis of the scientist's main publications on the history of the countries of Central and Eastern Europe. The applied research principles of historicism, scientific objectivity and systematicity contributed to highlighting the main aspects of J. Rychlík's diverse scientific work. The authors of the article note that for J. Rychlík history became one of the priority objects of scientific study after the Velvet revolution of 1989, when, under the conditions of democratization, historians of Czechoslovakia gained freedom of scientific creativity. Among the relevant research topics was the issue of relations between Czechs and Slovaks in 1918-1992. The scholar thoroughly researched their individual stages and, in particular, the period of the first Czechoslovak Republic 1918-1938 - one of the few democratic states of Central and Eastern Europe at that time. J. Rychlík deeply analyzed and assessed the trends of socio-political, economic, and cultural development of various regions of the First Republic, the peculiarities of interethnic relations, its international position, noted the positive role of this state in the history of the Czechs, Slovaks and Ruthenians-Ukrainians of Transcarpathia. Summarizing Czech-Slovak relations in general for the years 1918-1992, J. Rychlík considered one of the main reasons for the termination of the Czechoslovak state at the end of 1992 to be the failure to create a political Czechoslovak nation. The field of scientific interests of J. Rychlík also includes the national histories of the countries of Central and Eastern Europe, which resulted in the publication of a number of monographs on the past of the states of the region: Bulgaria (2000), Macedonia (2003), Croatia (2007), Slovenia (2011), the Czech Republic (2013), Ukraine (2015, 2022), Slovakia (2023), where the researcher was a co-author. In the conclusions of the article, the authors stated that J. Rychlík is one of the leading contemporary Czech researchers of the history of Central and Eastern European countries. The contribution of J. Rychlík to the study of the history of Czech-Slovak relations from 1918 to 1992 is especially significant. Jan Rychlík's extensive work on the history of the Czech and Slovak state is an important basis for further study of the past of the Czech Republic and the Slovak Republic in different periods.