The You River is the largest tributary of the Yuan River, one of main rivers in the Wuling Mountains in Southwest China. Its other name is Gengshi River ; it was called Youxi River in ancient times. Its trunk stream flows through Hubei, Chongqing and Hunan, and its drainage basin reaches into Guizhou. Its watershed covers an area of 19,254.3 square kilometres (7,434.1 sq mi), including 2,680.7 square kilometres (1,035.0 sq mi) of Hubei, 10,485.7 square kilometres (4,048.6 sq mi) of Hunan, 4,658.4 square kilometres (1,798.6 sq mi) of Chongqing and 1,519.5 square kilometres (586.7 sq mi) of Guizhou; it has a length of 484 kilometres (301 mi).