Dingxi, also known as Longyou is a prefecture-level city in the southeast of Gansu province, People's Republic of China. As of the 2020 census, its population was 2,524,097 inhabitants, of which 422,383 lived in the built-up area made of Anding urban district.

The Wei River is a major river in west-central China's Gansu and Shaanxi provinces. It is the largest tributary of the Yellow River and very important in the early development of Chinese civilization. In ancient times, such as in the Records of the Grand Historian, the river was called Wei Shui.