Yuanmousaurus ("Yuanmou lizard") was a sauropod dinosaur from the Middle Jurassic period of China. It is known from incomplete remains, recovered in 2000 from the Zhanghe Formation in Yuanmou County in Yunnan Province. Yuanmousaurus was a relatively large sauropod and may have reached about 17 meters (56 ft) in length. It was a basal member of the Sauropoda, but its exact systematic position is unclear. A recent study placed Yuanmousaurus within the family Mamenchisauridae. The only and type species was Yuanmousaurus jiangyiensis.