In 1985, the People’s Republic of Poland and the Soviet Union, now Poland and Russia respectively, established a maritime boundary in the Gulf of Gdansk and the Baltic Sea. Their maritime delimitation line is roughly equidistant, extends 90 nautical miles, and is composed of five turning points and two terminal points. It originates at the terminus point of the Poland–Russia land boundary on the coast of the Gulf of Gdansk and extends northward towards a tripoint between Poland, Russia, and Sweden in the Baltic Sea.

The maritime boundary between Poland and the Russian territory of Kaliningrad is notable for the fact that it was developed over numerous treaties dating from 1958 to 1985. While this border was established when the two States were politically aligned, since the fall of the communist governments that controlled both countries, their maritime border has managed to remain unaffected and uncontentious by the rather dramatic geopolitical shifts in the region.

Poland and Russia (Kaliningrad) also have an established land boundary.