Bohai Strait tunnel project in the context of "Liaodong Peninsula"

Northeast China (Chinese: 东北; pinyin: Dōngběi) is a geographical region of China, consisting officially of three provinces Liaoning, Jilin and Heilongjiang. The heartland of the region is the Northeast China Plain, the largest plain in China with an area of over 350,000 km (140,000 sq mi). The region is separated from the Russian Far East to the north and east by the Amur, Argun and Ussuri Rivers; from North Korea to the south by the Yalu and Tumen Rivers; and from the neighboring North China to the west by the Greater Khingan Range and Yan Mountains. It is also bounded by the Bohai Bay and Yellow Sea to the southwest, about 100 km (62 mi) away from East China's Jiaodong Peninsula across the Bohai Strait, due to be connected via a proposed undersea tunnel.

The four prefectures of Inner Mongolia (which is part of North China) east of the Greater Khingan, i.e. Chifeng, Tongliao, Hinggan and Hulunbuir, are sometimes also considered broader parts of Northeast China, and together with the aforementioned three provinces formed what was historically known as Inner Manchuria, in contrast to the Outer Manchuria (or "Outer Northeast" in Chinese literatures) annexed by the Russian Empire during the mid-19th century.