The purpose of the research is to study and analyze the Ukrainian nationalism theorists’ views of the interwar period of the XXth century concerning the place and role of Ukraine in the security system of the macroregion of Central and Eastern Europe, primarily in the context of developing mechanisms to deter the Russian aggression and the effective realization of its geopolitical potential. The methodology of the research is based on the methods of historicism, comparative analytical and structural system analysis, the principle of problem is applied. The scientific novelty consists in the fact that for the first time there has been elucidated a comprehensive vision of foreign policy directions of Ukraine’s development in the context of security problems of Central and Eastern Europe in the works of the Ukrainian nationalist thinkers of the interwar period of the XXth century. The Conclusions. In the 1920-ies and 1930-ies the Ukrainian nationalism theorists, determining Ukraine’s place in the security system of the macroregion of Central and Eastern Europe, considered the following components: Ukraine – Russia, Ukraine – Poland, Ukraine’s place in the confrontation with the Western-Eastern civilization, the security policy in the Baltic – the Black Sea region and foreign policy directions of the Black Sea region. According to the nationalist thinkers, Ukraine should carry out active foreign policy activities in the direction from the Baltic to the Caucasus and the Balkans. Furthermore, Turkey was determined as the main strategic ally of Ukraine among the countries of the Black Sea area, and Bulgaria was also potentially the closest ally among the Eastern Balkan state. It should be mentioned that allied relations with the South Caucasus countries as independent states were vital and the relations with Belarus were considered as a protective shield from the north. In addition, the Ukrainian thinkers are convinced that only a united Europe can withstand the Russian aggression and its potential geopolitical consequences. Consequently, in Ukrainian thinkers’ works Ukraine is given a central place in the security system on the eastern borders of the European continent and a role in countering Russia’s aggressive policy.