The Amur (река Амур, ɐˈmur), or Heilong Jiang (, Black Dragon River, hei1.long2-jiang1), is the world's tenth longest river, forming the border between the Russian Far East and Manchuria/Northeastern China. The Amur proper is long, and has a drainage basin of . Including its source river Argun, it is long. The largest fish species in the Amur is the kaluga, attaining a length as great as . The river basin is home to a variety of large predatory fish such as northern snakehead, Amur pike, taimen, Amur catfish, predatory carp and yellowcheek, as well as the northernmost populations of the Amur softshell turtle and Indian lotus.
The Russian name Amur comes the Tungusic term for “river”. Tungusic peoples are an ethno-linguistic group formed by the speakers of Tungusic languages (or Manchu–Tungus languages). They are native to Siberia and Northeast Asia.
Historically, it was common to refer to a river simply as "water". There are similar words for "water" or "river" in a number of Asiatic languages: e.g. 물 mul ("water") in Korean, muren or mörön ("river") in Mongolian, and 水 midu > mizu ("water") in Japanese. The name "Amur" may have evolved from a root word for water, coupled with a size modifier for "Big Water".
Its ancient Chinese names were Yushui, Wanshui and Heishui, with the latter name, meaning "black river", being the basis of the modern Chinese name Heilongjiang or "Black Dragon River", while the Manchurian name Sahaliyan Ula, the Mongolian names "Amar mörön" (Cyrillic: Амар мөрөн) originates from the name "Amar" meaning to rest and Khar mörön (Cyrillic: Хар мөрөн) mean Black River.
The river rises in the hills in the western part of Northeast China at the confluence of its two major affluents, the Shilka and the Argun (or Ergune), at an elevation of . It flows east forming the border between China and Russia, and slowly makes a great arc to the southeast for about , receiving many tributaries and passing many small towns. At Huma, it is joined by a major tributary, the Huma He.