The Argun or Ergune (Buryat: Эргэнэ гол, Ergene gol; Mongolian: Эргүнэ мөрөн, Ergüne mörön) is a 1,621 kilometres (1,007 mi) river that forms part of the eastern China–Russia border, together with the Amur River (Heilong Jiang). Its upper reaches are known as Hailar River (Chinese: 海拉尔河; pinyin: Hăilā'ěr Hé) in China. The Ergune marks the border (established by the Treaty of Nerchinsk in 1689) between Russia and China for about 944 kilometres (587 mi), until it meets the Amur River.