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 km2 (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.
Northeast China is one of the country's most important breadbaskets due to its fertile black soil, producing over 20% of China's total staple food production in 2020. It was also one of the first regions of China to undergo industrialization, and was the pioneering region during the planned economy era that followed the founding of the People's Republic of China, earning it the honorfic nickname "the Republic's eldest son" (Chinese: 共和国长子; pinyin: gònghéguó zhǎngzǐ). However since the Chinese economic reform of the 1980s, which had mostly benefited the coastal provinces in East and South China that have direct access to export sea routes and foreign investments, the Northeast's once-powerful industrial sector has shrunk significantly with stagnant economic growth, mass layoffs from state-owned enterprises during the late 1990s, and ongoing exodus of skilled population since the turn of the 21st century, leading to the region being often referred to as China's Rust Belt. To salvage the situation, an economic campaign named the Northeast Area Revitalization Plan was launched in 2003 by the State Council and the newly ascended Hu–Wen Administration, in which five prefectures of eastern Inner Mongolia, namely Hulunbuir, Hinggan, Tongliao, Chifeng and Xilin Gol, are also formally defined as regions of the Northeast.