Amdo (Tibetan: ཨ་མདོ་, Wylie: a mdo [ʔam˥˥.to˥˥]; Chinese: 安多; pinyin: Ānduō), also known as Domey (Tibetan: མདོ་སྨད་), is one of the three traditional Tibetan regions. It encompasses a large area from the Machu (Yellow River) to the Drichu (Yangtze). Amdo is mostly coterminous with China's present-day Qinghai province, but also includes small portions of Sichuan and Gansu provinces.

In the 7th century, Amdo became a part of the Tibetan Empire until its dissolution in the 9th century. A local Tibetan theocracy called Tsongkha ruled the region from 997 to 1104. In the 13th century, Mongol forces conquered the area, which led to the beginning of a priest and patron relationship. From the 14th to the 16th century, the Ming Dynasty controlled some border areas of Amdo while Mongol presence remained significant. In the 1720s, the Yongzheng Emperor of Qing dynasty seized Amdo from the Dzungars and began forming the modern boundaries of Qinghai. He allowed most of the area to be administered by a series of local Tibetan rulers associated with the Ü-Tsang government through monastery systems but not directly governed by the Dalai Lama's Ganden Phodrang. From 1917 parts of Amdo were occupied by warlords of the Ma clique, who joined the Kuomintang (Chinese Nationalist Party) in 1928. By 1952, Chinese Communist Party forces had annexed central Tibet and defeated both Kuomintang and Tibetan forces, solidifying their hold on the area roughly by 1958.

Tibetans in Amdo traditionally engaged in agriculture and pastoralism. The region is the home of many Tibetan Buddhism spiritual leaders, such as the 14th Dalai Lama, the 10th Panchen Lama Choekyi Gyaltsen, and the great Gelug school reformer Je Tsongkhapa.

Amdo is one of the traditional regions of Greater or ethnographic Tibet. The other regions are Ü-Tsang, also known as political or central Tibet, to the southwest and Kham to the south. The name Amdo has become more common since the nineteenth century; older sources refer to roughly the same region as Domey. Amdo and Kham together were also called Do Kham on maps and manuscripts.

Amdo encompasses the upper reaches of the Machu or Yellow River and Lake Qinghai. Its southern border is the Bayan Har Mountains. The area is wind-swept and tree-less, with much grass. Animals of the region consist of the wild yak and the kiang. Domesticated animals of the region consist of the domestic yak and dzo, goats, sheep, and the Mongolian horse. Amdo has been famous in epic story and in history as a land where splendid horses are raised and run wild.

In historical times, the people of the region were typically non-Tibetan, such as the Mongols or the Hor people, although the latter were able to speak a Tibetan language. Other indigenous peoples included the Qiang, the Sumpa, and the Tuyuhun. People from Amdo and Kham have traditionally identified themselves as Amdowas and Khampas rather than Tibetans, sometimes more connected to the Chinese than they were to Ü-Tsang (Central Tibet).

The inhabitants of Amdo are referred to as Amdowa (Tibetan: ཨ་མདོ་པ།, Wylie: a mdo pa) as a distinction from the Tibetans of Kham (Khampa, Tibetan: ཁམས་པ།, Wylie: khams pa) and Ü-Tsang, however, they are all considered ethnically Tibetan.^{[citation needed]}

Today, ethnic Tibetans predominate in the western and southern parts of Amdo, which are now administered as various Tibetan, Tibetan-Qiang, or Mongol-Tibetan autonomous prefectures. The Han Chinese are majority in the northern part (Haixi Mongol and Tibetan Autonomous Prefecture) and eastern part (Xining city and Haidong city) of Qinghai province. While Xining city and Haidong city are geographically small compared to the rest of Qinghai province, this area has the largest population density, with the result that the Han Chinese outnumber other ethnicities in Qinghai province generally.^{[citation needed]}