River, east-central Russia, one of the longest rivers in the world.
From its source in a Siberian mountain lake west of Lake Baikal , it flows 2,734 mi (4,400 km) north across Russia to enter the Arctic Ocean. Its basin covers an area of 961,000 sq mi (2,490,000 sq km), and it has many tributaries, including the Vitim and Olekma rivers. The land along its upper course and tributaries is rich in minerals, including gold and coal. Explorers first reached its delta on the Laptev Sea in the early 1630s.