Northeast China Plain

The Northeast China Plain or Northeast Plain (simplified Chinese: 东北平原; traditional Chinese: 東北平原; pinyin: Dōngběi Píngyuán), also known as the Manchurian Plain, is a lowland plain in Northeast Asia located in a vast, elongated basin formed by the Greater, Lesser and Outer Khingan Ranges. The modern term, especially in China, refers specifically to the Songliao Plain, which occupies the southern three-quarters of the basin within China–Russia border and forms the main portion of Northeast China (Inner Manchuria). It is bounded in the west by the Greater Khingan Range and northern/eastern branches of the Yan Mountains, in the east by the Lesser Khingan Range (which separates it from the Sanjiang Plain to the northeast) and western branches of Changbai Mountains (e.g. the Zhangguangcai Range and Qian Mountains), in the north by the Amur River (which separates it from the northern quarter of the basin outside the China–Russia border), and in the south by the Liaodong Bay of the Bohai Sea.

Covering approximately 350,000 km2 (140,000 sq mi), the Northeast Plain is China's largest plain. It consists of two primary alluvial plains, namely the Songnen Plain in the north, formed by the catchments of the Songhua River and its main tributary Nen River; and Liaohe Plain in the south, formed by the catchment of the Liao River and its former tributaries Hun and Taizi River. The watershed between the two plains is located among a series of low hills between Tongyu and Gongzhuling in central Jilin province. Although technically also a part of the broader Northeast Plain according to natural geography, the Zeya–Bureya plains on the left bank (north side) of the Amur River are excluded in modern political geography, as they were annexed by the Russian Empire in 1858 as part of the larger Outer Manchuria (a.k.a. "Russian Manchuria") region and now belong to the Amur Oblast of the Russian Federation's Far Eastern Federal District.

The Northeast Plain has a mostly flat topography with an average elevation lower than 200 m (660 ft), and less than 100 m (330 ft) in the southern coastal regions.