Marttila (Finnish pronunciation:[ˈmɑrtːilɑ]), Swedish:S:t Mårtens, i.e. Saint Martin′s) is a municipality of Finland.
It is located in the province of Western Finland and is part of the Southwest Finland region. The municipality has a population of 2,053 (30 June 2015) and covers an area of 195.98 square kilometres (75.67sqmi) of which 0.71km (0.27sqmi) is water. The population density is 10.51 inhabitants per square kilometre (27.2/sqmi).