Kauhajoki is a municipality of Finland.
It is located in the province of Western Finland and is part of the Southern Ostrobothnia region. The municipality has a population of 14,596 (2003) and covers an area of 1,315.46 kmē of which 15.68 kmē is water. The population density is 11.1 inhabitants per kmē.
The municipality is unilingually Finnish.
