Gar Tagu Risum (Tibetan: མགར་སྟ་གུ་རི་ཟུམ, Wylie: mgar sta gu ri sum, ?
According to Old Tibetan Annals, his eldest brother Gar Tsenye Dompu came into conflict with another minister Gar Mangnyen Taktsab in 685, and was killed by a river in Sumpa.
In 692, the Chinese troops led by Wang Xiaojie invaded Tibet in order to recapture the lost land: Four Garrisons of Anxi.
Tagu fought together with his brothers Trinring, Tsenyen Gungton, and Western Turks' khan Ashina Tuizi (阿史那俀子).
Two years later, Chinese invaded Tibet again, and defeated Tibetan troops near Qinghai Lake.