The Amur or Heilong Jiang (Even: Тамур (Tamur), Manchu: , Sahaliyan Ula; Chinese: 黑龙江; pinyin: Hēilóng Jiāng; Russian: река Аму́р, IPA: [ɐˈmur]) is the world's tenth longest river, forming the border between the Russian Far East (Outer Manchuria) and Northeastern China (Inner Manchuria).

It rises in the hills of western Manchuria at the confluence of its two major affluents, the Shilka River and the Ergune River, at an elevation of 303 metres (994 ft). It flows east forming the border between China and Russia, and slowly makes a great arc to the southeast for about 400 kilometres (250 mi), receiving many tributaries and passing many small towns. At Huma, it is joined by a major tributary, the Huma River. Afterwards it continues to flow south until between the cities of Blagoveschensk (Russia) and Heihe (China), it widens significantly as it is joined by the Zeya River, one of its most important tributaries.

The Amur arcs to the east and turns southeast again at the confluence with the Bureya River, then does not receive another significant tributary for nearly 250 kilometres (160 mi) before its confluence with its largest tributary, the Songhua River, at Tongjiang. At the confluence with the Songhua the river turns northeast, now flowing towards Khabarovsk, where it joins the Ussuri River and ceases to define the Russia-China border. Now the river spreads out dramatically into a braided character, flowing north-northeast through a wide valley in eastern Russia, passing Amursk and Komsomolsk-on-Amur. The valley narrows after about 200 kilometres (120 mi) and the river again flows north onto plains at the confluence with the Amgun River. Shortly after the Amur turns sharply east and into an estuary at Nikolayevsk-on-Amur, about 20 kilometres (12 mi) downstream of which it flows into the Strait of Tartary