Aldan, river, c.1,400 mi (2,250 km) long, rising in the Stanovoy Range, Sakha Republic, SE Siberian Russia. It flows north and east, past Tommot and around the Aldan Plateau, before flowing generally northwest to enter the Lena River c.100 mi (160 km) N of Yakutsk. The Amga, Uchur, and Maya rivers are its main tributaries. The Aldan River is navigable c.1,000 mi (1,610 km) upstream. Gold is found in its basin.