Amur (Amoor), or Sakhalin, a river formed by the junction of the Shilka and the Argun, which both come from the south-west - the former rising in the foothills of the Yablonoi Mountains. From the junction, the river flows 3000 miles south-eastward and north-eastward to the Sea of Okhotsk, opposite the island of Saghalien. Its main tributaries are the Sungari and the Usuri, both from the south. Above the Usuri, the Amur is the boundary between Siberia and Manchuria; below it, the river runs through Russian territory. It is very valuable for navigation, and carries a considerable fleet of steamers, but on account of the bar at its mouth, goods are generally disembarked, and carried overland to Alexandrovsk. The river is frozen for six months of the year; in summer there are extensive inundations.

From 1636, Russian adventurers made excursions into the Chinese territories of the Lower Amur.; but it was not until 1854-56 that two military expeditions established the stations of Alexandrovsk and Nikolaevsk. In 1858 China agreed to the treaty of Tientsin, by which the left bank of the Amur, and all the territory north of it, became Russian; and below the confluence of the Usuri, both banks. In 1860 Russia acquired the wide territory extending from the Amur and the Usuri to the Pacific coast, with harbours on the Pacific in a comparatively temperate latitude, where navigation is impeded by ice for not more than three or four months a year.

This vast territory falls into two Russian provinces - the Maritime Province between the Usuri and the sea, and the government of Amur, north of the river. The latter has an area of 172,850 sq. m., and a pop. of 122,640, mostly belonging to the Tungusic stock. The capital is, since 1882, Khabarovka, and not, as formerly, Blagovestschensk. Nikolaevsk, once the only important place in these regions, is on the Amur, 26 miles from its mouth, where the river is 1 1/4 mile wide, and in places 15 feet deep. Near the southern end of the Maritime Province (area, 715,980 sq. m.; pop. 221,750) is situated the important harbour of Vladivostok (' Rule of the East'), or Port May, which, in 1872, was placed in telegraphic communication with Europe by the China submarine cable. Vladivostok is one terminus of the Trans-Siberian railway commenced in 1891. The island of Saghalien (q.v.) is also a part of the Amur region in the wider sense.