abstract:Wang Gui (王珪) (571–639), courtesy name Shujie (叔玠), formally Duke Yi of Yongning (永寧懿公), was a chancellor during the reign of Emperor Taizong of Tang (Li Shimin). He had previously served Li Shimin's older brother Li Jiancheng the Crown Prince, with whom Li Shimin was locked in an intense rivalry during the reign of their father Emperor Gaozu, but after Li Shimin killed Li Jiancheng and then took the throne, he knew that Wang was faithful to Li Jiancheng and was capable, and therefore retained him, eventually making him chancellor.