Li Yuanji (李元吉) (603 – July 2, 626), formally Prince La of Chao (巢剌王), more commonly known by the title of Prince of Qi (齊王), nickname Sanhu (三胡), was an imperial prince of the Chinese Tang Dynasty. He was a son of the dynasty's founder Emperor Gaozu of Tang (Li Yuan), and in the intense rivalry developed between his older brothers Li Jiancheng the Crown Prince and Li Shimin the Prince of Qin, he sided with Li Jiancheng and often advocated drastic actions against Li Shimin, including assassination. In 626, Li Shimin, fearing that Li Jiancheng and Li Yuanji were about to kill him, laid an ambush for them at Xuanwu Gate outside the palace and killed them. Li Shimin then effectively forced Emperor Gaozu to yield the throne to him (as Emperor Taizong).
Read more about Li Yuanji: Background, Participation in Tang's Founding, Role in The Rivalry Between Li Jiancheng and Li Shimin, Death