Kut Bak (Thai: กุดบาก, pronounced [kùt bàːk]) is a district (amphoe) of Sakon Nakhon province, Thailand.

Neighboring districts are (from the north clockwise) Nikhom Nam Un, Phanna Nikhom, Mueang Sakon Nakhon, and Phu Phan of Sakon Nakhon Province, Kham Muang of Kalasin province and Wang Sam Mo of Udon Thani province.

The minor district (king amphoe) was created on 1 February 1964, when three tambons, Kut Bak, Khok Phu, and Na Mong were split from Mueang Sakon Nakhon district.

[2] The district is divided into three sub-districts (tambons), which are further subdivided into 38 villages (mubans).

Missing numbers are tambons which now form Phu Phan District.