Ziying () ( ? - end of January 206 BC) was the last ruler of the Qin Dynasty of China, ruling as King of Qin (秦王) from mid-October to the beginning of December 207 BC, and being known posthumously as Qin San Shi (秦三世, in full Qin San Shi Huangdi 秦三世皇帝, literally "the Third Emperor of Qin").

He was (according to historian Wang Liqun) probably one of Shihuangdi's brothers. He lured and killed the powerful chief eunuch Zhao Gao, who was prime minister and had murdered Ziying's nephew Qin Er Shi. He then surrendered to Liu Bang -- the first rebel leader to enter the capital Xianyang and then later founder of Han Dynasty. He was only on the throne for 46 days. He was soon killed after Liu Bang handed him over to the most powerful rebel of the time, Xiang Yu.

The identity of Ziying

The Shiji does not specify his age. It implies that he has at least two sons, when it says that Ziying consulted with them. This suggests that Ziying simply can't be the son of Fusu (as some people have suggested). In Wang Liqun's analysis, he reasoned that the maximum possible age so that Ziying could've been both the son of Fusu and have two fully grown sons is 19. Therefore, his two sons would been around 1-2 years old. Therefore, he couldn't have consulted with his sons, and by this logic, he can only be the uncle of Ershi, and not the son of Fusu.