Amur, river, east central Asia, formed by the junction of the Shilka and Argun rivers. The Amur flows southeast, forming the border between Russia and China for almost 1,610 km (1,000 mi). It then flows northeast and empties into Tatar Strait (Tatarskiy Proliv) near the city of Nikolayevsk-na-Amure. Some 2,874 km (1,786 mi) long, the Amur is one of the great rivers of the world. Including the chief headstreams, the total system has a length of about 4,416 km (2,744 mi). The Amur is navigable throughout its entire course, and the Shilka is navigable to Sretensk, Russia. The Amur is closed to navigation for about six months in winter. Among the major tributaries are the Zeya, Songhua, Ussuri, and Bureya rivers. Important Chinese towns on the Amur River, known in Chinese as Heilong Jiang (Hei-lung Chiang), include Aihui (Heihe) and Tongjiang (T'ung-chiang). Besides Nikolayevsk-na-Amure, the principal Russian cities on the river are Blagoveshchensk, Khabarovsk, and Komsomol’sk-na-Amure.