The Kotra is a 109-kilometre-long (68 mi) river in Belarus and Lithuania. The river is an example of a rare phenomenon of river bifurcation.

The Belarus–Lithuania border is an international border almost 678.8 km (421.8 mi) in length between the Republic of Belarus and the Republic of Lithuania. It is an external border of the European Union as well as the western border of the Commonwealth of Independent States. 379.9 km (236.1 mi) of the border is on land, while 298.9 km (185.7 mi) are on water, crossing lakes, e.g. Lake Drūkšiai and following some rivers, e.g. Dysna River and Neman River.