Manchuria is a term that refers to a region in Northeast Asia encompassing the entirety of present-day Northeast China, and historically parts of the modern-day Russian Far East, often referred to as Outer Manchuria. Its definition may refer to varying geographical extents as follows: the Chinese provinces of Heilongjiang, Jilin, and Liaoning but broadly also including the eastern Inner Mongolian prefectures of Hulunbuir, Hinggan, Tongliao, and Chifeng, collectively known as Northeast China; the aforementioned regions plus the homelands of ancient Jurchen and their descendant Manchus, parts of these region were ceded to the Russian Empire by the Manchu-led Qing dynasty during the Amur Annexation of 1858–1860, which include present-day Amur Oblast, Primorsky Krai, the Jewish Autonomous Oblast, the southern part of Khabarovsk Krai, and the eastern edge of Zabaykalsky Krai, collectively known as the Outer Manchuria or Russian Manchuria.

Northeast China is a geographical region of China, also called Manchuria in history. It usually corresponds specifically to the three provinces east of the Greater Khingan Range, namely Liaoning, Jilin, and Heilongjiang, but historically is meant to also encompass the four easternmost prefectures of Inner Mongolia west of the Greater Khingan. The heartland of the region is the Northeast China Plain, the largest plain in China, with an area of over 350,000 km2 (140,000 sq mi). It is separated from the Russian Far East to the north by the Amur, Argun, and Ussuri Rivers; from Korea to the south by the Yalu and Tumen Rivers; and from Inner Mongolia to the west by the Greater Khingan and parts of the Xiliao River.