Kosum Phisai (Thai: โกสุมพิสัย, pronounced [kōː.sǔm pʰí.sǎj]) is a district (amphoe) in the northern part of Maha Sarakham province, northeastern Thailand.

Neighboring districts are (from the north clockwise): Chiang Yuen, Kantharawichai, Mueang Maha Sarakham, Borabue, and Kut Rang of Maha Sarakham Province: Ban Phai, Ban Haet, and Mueang Khon Kaen of Khon Kaen province.

Kosum Phisai is divided into 17 sub-districts (tambons), which are further subdivided into 235 administrative villages (mubans).

There is one sub-district municipality (thesaban tambon) in the district: There are 17 sub-district administrative organizations (SAO) in the district:

This Maha Sarakham Province location article is a stub.