East Prussia – a former province of the German Reich – has not been in existence since 1945 but continues to breed conflicts of national mental geographies based on different approaches to imagining nation. Part of Lithuanian society perceives the Kaliningrad region of the Russian Federation (former Prussian Königsberg) as “Little Lithuania,” the ancient cradle of Lithuanian culture. In Russia, a number of top politicians are mobilizing public opinion to claim the northern part of former East Prussia – now the Klaipėda region within Lithuania – as a legitimate territory of Russia. The article examines the specific historic and cultural contexts in Lithuania and Russia that made these claims possible. The author concludes that the conflict between the Russian and Lithuanian spatial imaginations is a result of different approaches to imagining national territories: one based on the ethnographic principle and the other on the principle of legitimate conquest.