Xinjiang lies in the north-west of China and is the country's biggest region.
Like Tibet, it is autonomous, meaning - in theory - it has some powers of self-governance. But in practice, both face major restrictions by the central government.
It is a mostly desert region, producing about a fifth of the world's cotton.
It is also rich in oil and natural gas and because of its proximity to Central Asia and Europe is seen by Beijing as an important trade link.
In the early 20th Century, the Uighurs briefly declared independence, but the region was brought under the complete control of China's new Communist government in 1949.