The Treaty of Aigun was signed by Russia and the Qing Empire on May 28, 1858 in the Manchurian town of Aigun.

This treaty was one of many unequal treaties between Imperial China and foreign powers in the 19th and early 20th centuries. These treaties forced China to concede many territorial and sovereignty rights. The purpose of the treaty was to establish a border along the Amur River. According to this treaty, Russia regained the left bank of the Amur River lost the ancient Hulun Manchu territory to China as a result of Nerchinsk Treaty of 1689. This treaty and the Beijing Treaty of 1860 established the modern borders of the Russian Far East.