Zhangsun Wuji (died 659), courtesy name Fuji, formally Duke of Zhao, is a chancellor of the Chinese dynasty Tang Dynasty during the reigns of his brother-in-law Emperor Taizong (Li Shimin) (husband of his sister Empress Zhangsun) and nephew Emperor Gaozong (Li Zhi).

He is an important assistant of Li Shimin when Li Shimin is the Prince of Qin under his father Emperor Gaozu and helps Li Shimin in killing his rivals and brothers Li Jiancheng the Crown Prince and Li Yuanji the Prince of Qi at the Xuanwu Gate Incident, eventually enabling Li Shimin to become emperor.

He is also instrumental in Emperor Taizong's selection of Li Zhi as crown prince, and is exceedingly powerful after Li Zhi takes the throne as Emperor Gaozong.

However, he gradually loses his nephew's favor by failing to support Emperor Gaozong's decision to depose his first wife Empress Wang and replacing her with Empress Wu.

In 659, Empress Wu's political ally Xu Jingzong falsely accuses Zhangsun of treason, and Emperor Gaozong exiles Zhangsun.

Xu subsequently sends the official Yuan Gongyu to force Zhangsun to commit suicide.