Kortesjärvi is a former municipality of Finland. It was consolidated, together with Alahärmä and Ylihärmä, to Kauhava on 1 January 2009.

It is located in the province of Western Finland and is part of the Southern Ostrobothnia region. The municipality had a population of 2,275 (as of 31 December 2008) and covered a land area of 323.70 square kilometres (124.98 sq mi). The population density was 9.81 inhabitants per square kilometre (25.4/sq mi).

The municipality was unilingually Finnish.