The Shagan (Kazakh: Шаған - Şağan; Russian: Чаган - Chagan), is a river in the Zhanasemey, Abai and Beskaragay districts of Abai Region, east Kazakhstan.

[1] The Shagan has its sources in the northwestern slopes of the Chingiztau, a subrange of the Kazakh Uplands.

Finally it meets the left bank of the Irtysh 275 km (171 mi) to the west of Semey, former Semipalatinsk, city.

Its food is mainly snow and the river is under ice between November and April.

Its main tributary is the Ashchysu from the right,[2][1] The lower course of the Shagan is located in the Balapan Complex area of the Semipalatinsk Polygon, the primary testing venue for the Soviet Union's nuclear weapons.