Inner Mongolia, officially the Inner Mongolia Autonomous Region, is an autonomous region of China. Its border includes two-thirds of the length of China's border with the country of Mongolia. Inner Mongolia also accounts for a small section of China's border with Russia (Zabaykalsky Krai). Its capital is Hohhot; other major cities include Baotou, Chifeng, Tongliao and Ordos.

The autonomous region was established in 1947, incorporating the areas of the former Republic of China provinces of Suiyuan, Chahar, Rehe, Liaobei, and Xing'an, along with the northern parts of Gansu and Ningxia.

Its area makes it the third largest Chinese administrative subdivision, constituting approximately 1,200,000 km² (463,000 sq mi) and 12% of China's total land area. Due to its long span from east to west, Inner Mongolia is geographically divided into eastern and western divisions. The eastern division is often included in Northeastern China (Dongbei), with major cities including Tongliao, Chifeng, Hailar, and Ulanhot. The western division is included in North China, with major cities including Baotou and Hohhot. It recorded a population of 24,706,321 in the 2010 census, accounting for 1.84% of Mainland China's total population. Inner Mongolia is the country's 23rd most populous province-level division. Han Chinese make up the majority of the population in the region; Mongols constitute a significant minority with over 4 million people, making it the largest Mongol population in the world (larger than that of the country Mongolia). Inner Mongolia is one of the more economically developed provinces in China with annual GDP per capita at US$14,343 (2022), ranked 8th in the nation. The official languages are Mandarin and Mongolian, the latter of which is written in the traditional Mongolian script, as opposed to the Mongolian Cyrillic alphabet, which is used in the country of Mongolia, formerly described as Outer Mongolia.

In Chinese, the region is known as "Inner Mongolia", where the terms of "Inner" and "Outer" are derived from Manchu dorgi and tulergi (cf. Mongolian dotugadu and gadagadu). Inner Mongolia is distinct from Outer Mongolia, which was a term used by the Republic of China and previous governments to refer to what is now the independent state of Mongolia and the Republic of Tuva in Russia. The term Inner 内 (Nei) referred to the Nei Fan 内藩 (Inner Tributary), i.e., those descendants of Genghis Khan who were granted the title khan (king) in the Ming and Qing dynasties and lived in part of southern Mongolia.

Due to the perceived Sinocentric nature of the name "Inner Mongolia", some Mongols outside of China, particularly those in the state of Mongolia and separatist groups in the West, prefer the name "Southern Mongolia". However, this name has not been adopted officially by any government bodies.

Much of what is known about the history of the Mongolian Plateau is taken from Chinese chronicles and historians. Before the rise of the Mongols in the 13th century, what is now central and western Inner Mongolia, especially the Hetao region, alternated in control between Chinese farming communities in the south, and Xiongnu, Xianbei, Khitan, Jurchen, Tujue, and nomadic Mongol of the north. The historical narrative of what is now Eastern Inner Mongolia mostly consists of alternations between different Tungusic and Mongol tribes, rather than the struggle between nomads and Chinese farmers.

Slab Grave cultural monuments are found in Northern, Central and Eastern Mongolia, Inner Mongolia, North-Western China, Southern, Central-Eastern and Southern Baikal territory. Mongolian scholars prove that this culture related to the Proto-Mongols.

During the Zhou dynasty, Central and Western Inner Mongolia (the Hetao region and surrounding areas) were inhabited by nomadic peoples such as the Loufan, Linhu and Dí, while Eastern Inner Mongolia was inhabited by the Donghu. During the Warring States period, King Wuling (340–295 BC) of the state of Zhao based in what is now Hebei and Shanxi Provinces pursued an expansionist policy towards the region. After destroying the Dí state of Zhongshan in what is now Hebei province, he defeated the Linhu and Loufan and created the Yunzhong Commandery near modern Hohhot. King Wuling of Zhao also built a long wall stretching through the Hetao region. After Qin Shi Huang created the first unified Chinese empire in 221 BC, he sent the general Meng Tian to drive the Xiongnu from the region and incorporated the old Zhao wall into the Qin dynasty Great Wall of China. He also maintained two commanderies in the region: Jiuyuan and Yunzhong and moved 30,000 households there to solidify the region. After the Qin dynasty collapsed in 206 BC, these efforts were abandoned.