Ergune or Argun (Mongolian: Эргүнэ мөрөн, Ergüne mörön; Manchu: ; ; ) is the river which is a part of the Russia–China border. Its upper reaches are known as Hailar River in China. Its length is . The Ergune marks the border (established by the Treaty of Nerchinsk in 1689) between Russia and China for about , until it meets the Amur River. The name derives from Buryat Urgengol 'wide river' (urgen 'wide' + gol 'river'). Mongolian word "ergün" (in Traditional Mongolian alphabet) or "örgön" (in modern Mongolian) means "wide". The river flows from the Western slope of the Greater Khingan Range in Inner Mongolia. Its confluence with Shilka River at Ust-Strelka forms the Amur River.