The Battle of Irtysh River or Battle of Yexi River is a battle in 657 between Tang Dynasty general Su Dingfang and the Western Turkic Khaganate qaghan Ashina Helu during the Tang campaign against the Western Turks.

It is fought along the Irtysh River near the Altai Mountains.

Helu's forces, consisting of 100,000 cavalry, are ambushed by Su as Helu chases decoy Tang troops that Su had deployed.

Helu is defeated during Su's surprise attack, and loses most of his soldiers.

Turkic tribes loyal to Helu surrender, and the retreating Helu is captured the next day.

Helu's defeat ends the Western Turkic Khaganate, strengthens Tang control of Xinjiang, and leads to Tang suzerainty over the western Turks.