Isokyrö (Swedish:Storkyro) is a municipality of Finland.
It is located in the province of Western Finland and is part of the Ostrobothnia region. The municipality has a population of 4,831 (30 June 2015) and covers an area of 356.99 square kilometres (137.83sqmi) of which 2.79km (1.08sqmi) is water. The population density is 13.64 inhabitants per square kilometre (35.3/sqmi).