The Lena is a river in the Russian Far East and is the easternmost river of the three great rivers of Siberia which flow into the Arctic Ocean, the others being Ob and Yenisey. The Lena River is 4,294 km (2,668 mi) long and has a capacious drainage basin of 2,490,000 km2 (960,000 mi2); thus the Lena is the eleventh-longest river in the world and the longest river entirely within Russia. Geographically, permafrost underlies all the Lena River's catchment and it is continuous in over 75 percent of the basin.
