Ziying, King of Qin^{[lower-alpha 1]} (Chinese: 秦王子嬰; pinyin: Qín-wáng Zǐyīng, died c.January 206 BC^[2]) was the third and last ruler of the Qin dynasty. He ruled over a fragmented Qin Empire for 46 days, from mid-October to early December 207  BC. He is referred to in some sources with the posthumous name Emperor Shang of Qin (秦殤帝) although Qin abolished the practice of posthumous names. (In Chinese tradition, even someone who never held a ruling title while he was alive might be given the posthumous title "emperor" after his death.)

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There is no firm consensus as to what Ziying's relationship to the Qin royal family really was.

He is mentioned in historical records as either:

1. A son of Qin Er Shi's elder brother (who, according to Yan Shigu's commentaries,^[3][4] was Fusu);^[5]

   二世三年，赵高杀二世后，立二世之兄子公子婴为秦王。
   In the third year of [Qin] Er Shi (207 BCE), Zhao Gao, after killing [Qin] Er Shi, installed [Qin] Er Shi's elder brother's son Prince Ying as the King of Qin.

   — Sima Qian, Records of the Grand Historian, "Records of Qin Shi Huang"

2. An elder brother of Qin Er Shi;^[6]

   三赵高反，二世自杀，高立二世兄子婴。
   In the third year [of Qin Er Shi], [Zhao] Gao made a coup d'etat, [Qin] Er Shi committed suicide, and [Zhao] Gao crowned [Qin] Er Shi's elder brother Ziying.

   — Sima Qian, Records of the Grand Historian, "Chronology of the Six States"

3. A younger brother of Qin Shi Huang;^[7] or

   叙述赵高杀二世后，引皇帝玺自佩，有篡位的意图，左右百官都不跟从，于是高自知天弗与，群臣弗许，乃召始皇弟，授之玺。子婴即位，患之，乃称疾不听事，与宦者韩谈及其子谋杀高。
   It is said that Zhao Gao, after killing [Qin] Er Shi, took the Emperor's Seal and had the intention to usurping the throne, but none of the courtiers would join his cause. And so [Zhao] Gao, knowing that his actions were not accepted by Heaven and not supported by the courtiers, summoned [Qin] Shi Huang's younger brother to give him the [Imperial] Seal. Ziying ascended the throne, but was concerned, and claimed illness to remain absent from court, conspiring with the eunuch Han Tan [zh] to assassinate [Zhao] Gao.

   — Sima Qian, Records of the Grand Historian, "Chronicle of Li Si"

4. A son of a younger brother of Qin Shi Huang.^[8]

   乃召始皇弟子婴，授之玺。
   ... summoned [Qin] Shi Huang's younger brother's son Ying to give him the [Heirloom] Seal.

   — Xu Guang [zh], Commentaries on Sima Qian's Records of the Grand Historian, "Chronicle of Li Si"

While Sima Qian's Records of the Grand Historian does not specify Ziying's age, it implies that he had at least two sons, whom he consulted.

After Qin Er Shi's death, Zhao Gao chose Ziying to be successor and changed the ruling title "emperor" back to "king" because the Qin dynasty then was as weak as the former Qin State, which no longer ruled the whole of China but held onto only Guanzhong.

Ziying was the only person in the Qin imperial court to defend and to try to persuade Qin Er Shi against the wrongful executions of Meng Tian and Meng Yi. He lured Zhao Gao, the regent who had assassinated Qin Er Shi, into a trap and killed him. Ziying later surrendered to Liu Bang, the leader of the first group of rebel forces to occupy Xianyang, the Qin capital. He was eventually killed, along with his male family members, by another rebel leader, Xiang Yu.

Ziying sometimes appears as a door god in Chinese and Taoist temples, usually paired with his successor, Emperor Yi of Chu.