Qinghai is an inland province in Northwestern China. It is the largest province of China (excluding autonomous regions) by area and has the third smallest population with its capital and largest city being Xining.

Qinghai borders Gansu on the northeast, Xinjiang on the northwest, Sichuan on the southeast and the Tibet Autonomous Region on the southwest. Qinghai province was established in 1928 during the period of the Republic of China, and until 1949 was ruled by Chinese Muslim warlords known as the Ma clique. The Chinese name "Qinghai" is after Qinghai Lake, the largest lake in China. The lake is known as Tso ngon in Tibetan, and as Kokonor Lake in English, derived from the Mongol Oirat name for Qinghai Lake. Both Tso ngon and Kokonor are names found in historic documents to describe the region.

Located mostly on the Tibetan Plateau, the province is inhabited by a number of peoples including the Han (concentrated in the provincial capital of Xining, nearby Haidong, and Haixi), Tibetans, Hui, Mongols, Monguors, and Salars. According to the 2021 census reports, Tibetans constitute a fifth of the population of Qinghai and the Hui compose roughly a sixth of the population. There are over 37 recognized ethnic groups among Qinghai's population of 5.6 million, with national minorities making up a total of 49.5% of the population.

The area of Qinghai came under the control of the Manchu-led Qing Dynasty around 1724, after their defeat of Khoshut Mongols who previously controlled most of the area. After the Xinhai Revolution and the ensuing fall of the Qing dynasty in 1912, Qinghai came under Chinese Muslim warlord Ma Qi's control until the Northern Expedition by the Republic of China consolidated central control in 1928. In the same year, the province of Qinghai was established by the Nationalist Government, with Xining as its capital.

During the Bronze Age, Qinghai was home to a diverse group of nomadic tribes closely related to other Central Asians who traditionally made a living in agriculture and husbandry, the Kayue culture. The eastern part of the area of Qinghai was under the control of the Han dynasty about 2,000 years ago. It was a battleground during the Tang and subsequent Central Plain dynasties when they fought against successive Tibetan tribes.

In the middle of 3rd century CE, nomadic people related to the Mongolic Xianbei migrated to pasture lands around the Qinghai Lake (Koko Nur) and established the Tuyuhun Kingdom.

In the 7th century, the Tuyuhun Kingdom was attacked by both the Tibetan Empire and the Tang dynasty as both sought control over the Silk Road trade routes. Tibetan King Songtsen Gampo was victorious, and settled the area around Tso ngon (Lake Go, or Kokonor Lake). Military conflicts had severely weakened the Tuyuhun kingdom and it was incorporated into the Tibetan Empire. The Tibetan Empire continued expanding beyond Tso ngon during Trisong Detsen's and Ralpacan's reigns, and the empire controlled vast areas north and east of Tso ngon until 848, which included Xi'an.

During the fragmentation of the Tibetan Empire, a series of local polities emerged under the political jostling of Western Xia to the north and Song dynasty to the east – from the military-rule of Guiyi Circuit, to a Tibetan tribal confederacy, and eventually the Tibetan theocratic kingdom of Tsongkha. The Song dynasty eventually defeated the Kokonor kingdom Tsongkha in the 1070s. During the Mongol-led Yuan dynasty's administrative rule of Tibet, the region comprised the headwaters of the Ma chu (Machu River, Yellow River) and the Yalong (Yangtze) rivers and was known as Amdo, but apportioned to different administrative divisions than Tibet proper.