Lithuania–Russia border in the context of "Širvinta (Šešupė)"

The Neman (based on Russian spelling), Nioman (Belarusian), Nemunas (Lithuanian), Niemen (Polish), or Memel (German), is a river in Europe that rises in central Belarus and flows through Lithuania then forms the northern border of Kaliningrad Oblast, Russia's western exclave, which specifically follows its southern channel. It drains into the Curonian Lagoon, narrowly connected to the Baltic Sea. The 937 km (582 mi) long Neman is a major Eastern European river. It flows generally west to Grodno within 12 kilometres (7.5 mi) of the Polish border, north to Kaunas, then westward again to the sea.

The largest river in Lithuania, and the third-largest in Belarus, it is navigable for most of its length. It starts from two small headwaters merging about 15 kilometers (9 mi) southwest of the town of Uzda – about 55 km (34 mi) southwest of capital city Minsk. Only 17 kilometres (11 mi), an eastward meander, contributes to the Belarus–Lithuania border. Thereafter the river includes notable loops along a minor tectonic fault.

The Šešupė (pronounced [ˈʃɛːʃʊːpeː] ); Russian: Шешупе; Polish: Szeszupa; German: Scheschup(p)e, Ostfluss) is a 298 km long river that flows through Poland (27 km), Lithuania (158 km), and Russia (62 km). The river flows for 51 km along the border between the Kaliningrad Oblast, an exclave of Russia, and Lithuania. The Šešupė originates near the Polish village of Szeszupka, about 16 km from the Polish-Lithuanian border, and flows into the Nemunas, near the town of Neman, on the border between Lithuania and Kaliningrad Oblast.

Major towns and cities along the river, from the Nemunas to the source, are: Kudirkos Naumiestis, Pilviškiai, Marijampolė, and Kalvarija.