The article discusses the origin and development of the Polish geopolitical concept - “Intermarium”, which is based on the idea of creating a large-scale interstate association in the geopolitical space of Central and Eastern Europe. In its various interpretations, this concept has always been associated with the confrontation with Russia, starting with the forerunner of the Intermarium - the Jagiellonian idea. The most serious attempts to realize these aspirations were made by Józef Piłsudski, who created the Intermarium concept, along with which he tried to implement the federalist project of 1918-1921 and the geopolitical project of “Prometheism”. Subsequently, the followers of these ideas, Jozef Beck and Jerzy Giedroyc, together with Juliusz Mieroszewski, tried to rebuild the legacy of Pilsudski's geopolitical thought in terms of the changing realities of the 20th century. Reliance on the Jagiellonian idea and its anti-Russian ambitions inevitably led all subsequent attempts to create such a geopolitical bloc to collapse. Nevertheless, this concept has been updated in Poland’s modern geopolitical strategy, although it is positioned exclusively as an integration economic and political project - the Three Seas Initiative (Trimarium). The authors analyse Poland's geopolitical perception of the region of Central and Eastern Europe and reveal the continuity in the Polish geopolitical thought and the idea of regional dominance in the space of the three seas. Based on the history of the evolution of the Intermarium concept, the authors focus on the fact that the modern Trimarium project is a new vision of old geopolitical aspirations.