Mellilä () is a former municipality of Finland. It was merged to the town of Loimaa on 1 January 2009.
It is located in the province of Western Finland and is part of the Southwest Finland region. The municipality had a population of 1,255 (2004-12-31) and covered an area of 110.62 km<sup>2</sup> of which 0.10 km<sup>2</sup> is water. The population density was 11.35 inhabitants per km<sup>2</sup>.
The municipality was unilingually Finnish.