The Kauylzhyr (Kazakh: Қауылжыр; Russian: Каульжур) is a river in Shalkar District, Aktobe Region, Kazakhstan.

[1] The river is part of the Shalkar Basin.

[1] The Kauylzhyr has its sources on the southeastern slopes of the Mugalzhar Hills.

In its final stretch it bends southwards and enters lake Shalkar from the north.

The main tributaries of the Kauylzhyr are the Alabassay, Karabulaksay, Sarysay and Koganzhar.