Kauhajoki is a town and municipality of Finland. It is located in the province of Western Finland and is part of the Southern Ostrobothnia region, 59 kilometres (37 mi) southwest of the city of Seinäjoki. The population of Kauhajoki is 12,618 and the municipality covers an area of 1,298.98 km2 (501.54 sq mi) of which 16.46 km2 (6.36 sq mi) is inland water. The population density is 9.71/km2 (25.1/sq mi). The town is unilingually Finnish.

South Ostrobothnia is one of the 19 regions of Finland. It borders the regions of Ostrobothnia, Central Ostrobothnia, Central Finland, Pirkanmaa, and Satakunta. Among the Finnish regions, South Ostrobothnia is the ninth largest in terms of population. Seinäjoki is the regional centre and by far the largest city in the area.