The Wei River (Chinese: 渭河; pinyin: Wèi Hé; Wade–Giles: Wei Ho) 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.The source of the Wei River is close to Weiyuan County – Wei yuan meaning "Wei's source" – in Gansu province, less than 200 kilometres (120 mi) from the Yellow River at Lanzhou.