Merimasku is a former municipality in the Southwest Finland region of Finland. It was consolidated, together with Rymättylä and Velkua, into the town of Naantali on January 1, 2009, and since then it has formed part of Naantali rather than existing as an independent municipality.
Before the merger, Merimasku bordered the municipalities of Askainen, Lemu, Masku, Naantali, Rymättylä and Velkua. Its location in the archipelago and coastal area of Southwest Finland places it within the wider Turku region.