Lithuania–Poland border

The current Lithuania–Poland border exists since the re-establishment of the independence of Lithuania on March 11, 1990. Until then the identical border was between Poland and Lithuanian SSR of the Soviet Union. The length of the border is 104 kilometres (65 mi). It runs from the Lithuania–Poland–Russia tripoint southeast to the Belarus–Lithuania–Poland tripoint.

It is the only land border that the EU- and NATO-member Baltic states share with a country that is not a member of the Russian-aligned Commonwealth of Independent States.

To the military planners of NATO, the border area is known as the Suwalki gap (named after nearby town of Suwałki), because it represents a tough-to-defend flat narrow piece of land, a gap, that is between Belarus and Russia's Kaliningrad enclave and that connects the NATO-member Baltic States to Poland and the rest of NATO. This view was reflected in a 2017 NATO exercise, which for the first time focused on defense of the gap from a possible Russian attack.

Map of Poland from the early 11th century shows Polish and Lithuanian lands separated by Old Prussian and Kievan Rus' territories

Map of Poland in the first half of the 13th century, shows a border between Duchy of Masovia and Lithuania

Map of Poland and Lithuania around 1275–1300, with visible Polish–Lithuanian border

Map of Poland and Lithuania around 1333–1370, with visible Polish–Lithuanian border

Map of Poland and Lithuania around 1370–1382, with visible Polish–Lithuanian border

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