Lieto is a town and municipality in Finland. It is located in the Southwest Finland region, in the southwestern part of the country.
As a municipality, Lieto forms part of the local government structure of Southwest Finland, one of the nineteen regions of Finland. The area around it belongs to the historic province of Finland Proper, the southwestern coastal district whose Finnish name is Varsinais-Suomi.
Lieto lies inland from the coast, within the wider Turku sub-region, the area centred on the city of Turku. The municipality is one of several smaller centres that surround Turku, the regional capital and the country's oldest city.