Zhaltyrsor (Kazakh: Жалтырсор) is a lake in Amangeldi District, Kostanay Region, Kazakhstan.

The lake lies at an elevation of 124 meters (407 ft) within the floodplain of the Tenteksay (Тентексай), a tributary of the Turgay, and is connected to it during spring floods.

Lake Katpagan lies 29 kilometers (18 mi) to the southeast.

In the summer the level of the lake sinks and it becomes a salt marsh.

[2][3] The lake basin is surrounded by steppe vegetation and is used as a pasture for local cattle.