The Lena is a river in the Russian Far East, and is the easternmost of the three great Siberian rivers that flow into the Arctic Ocean. The Lena is the eleventh-longest river in the world, and the longest river entirely within Russia, with a length of 4,294 km (2,668 mi) and a drainage basin of 2,490,000 km2 (960,000 sq mi). Permafrost underlies most of the catchment, 77% of which is continuous.

The Vitim is a major tributary of the Lena. Its source is east of Lake Baikal, at the confluence of rivers Vitimkan from the west and China from the east. The Vitim flows first south, bends eastwards and then northward in the Vitim Plateau. Then it flows north through the Stanovoy Highlands and the town of Bodaybo. Including river Vitimkan, its western source, it is 1,978 kilometres (1,229 mi) long, and has a drainage basin of 225,000 square kilometres (87,000 sq mi).