The Aksu (Kazakh: Ақсу, Aqsu; Russian: Аксу) is a river of the Balkhash-Alakol Basin, Kazakhstan.

It originates in the Dzungarian Alatau Mountains near the border with China and flows into Lake Balkhash.

The Aksu is one of the main rivers of the historic region of Zhetysu.

[2] The river flows north from the border with China before turning north-westward, passing by Matay and then northward when it reaches the Saryesik-Atyrau Desert, a large sand desert south of Lake Balkhash.

Because of irrigation, the river's flow into Lake Balkash is limited.