Lithuania's geography is defined by its connection to the Baltic Sea and a network of rivers and lagoons:
Forms Lithuania's western coastline (90 km / 56 mi). It's a brackish, inland sea connected to the Atlantic via the Danish Straits. Key port: Klaipėda. Borders 9 countries total.
A large, shallow lagoon separated from the Baltic by the Curonian Spit (a UNESCO World Heritage sand dune peninsula). The Klaipėda Strait connects it to the sea. The northern half belongs to Lithuania; the southern half to Russia's Kaliningrad Oblast. Famous for beaches, dunes, and the historic resort town of Nida.
Lithuania's longest river (937 km total, 475 km in Lithuania). Rises in Belarus, flows through southern Lithuania (Kaunas), forms part of the border with Kaliningrad, and drains into the Curonian Lagoon. Vital for transport, hydroelectric power (Kaunas Dam), and fishing.
The second-longest (234 km in Lithuania). Also originates in Belarus, flows through the capital Vilnius, and joins the Nemunas at Kaunas. Important for recreation, water supply, and history.
Other notable waters include the Minija, Šventoji, and Dubysa rivers, and numerous glacial lakes in the Aukštaitija National Park region.