Merikarvia (Swedish: Sastmola) is a municipality of Finland.
It is located in the Satakunta region. The neighboring municipalities are Isojoki, Kristiinankaupunki, Pomarkku, Pori and Siikainen.
The municipality has a population of 3,241 (30 June 2015) and it covers an area of 1,246.24 square kilometres (481.18 sq mi), of which 800.2 km2 (309.0 sq mi) is water. The population density is 7.27 inhabitants per square kilometre (18.8/sq mi).
The municipality is unilingually Finnish. The coastline was formerly swedishspeaking. Merikarvia is known by the Oura Archipelago, which is part of the Bothnian Sea National Park.
The area has been inhabited since as early as 1800 BC. There are grave sites from the Bronze and Iron Ages within the municipality. Most of the cairns are located in Tuorila village located east of the municipal center.
The birth of the earliest villages in Merikarvia - Kasala, Riispyy, Ala- and Yli-Kylä, and Köörtilä - is dated to between the 13th and 14th centuries. As a separate municipality, Merikarvia has existed since 1865.