Masainas is a town and comune located in the Province of Sulcis Iglesiente within the autonomous island region of Sardinia, Italy. It is situated in the traditional region of Sulcis, approximately 45 kilometres southwest of Cagliari and about 15 kilometres southeast of Carbonia.
The municipality has a population of 1,203 inhabitants. It serves as a local administrative center within its specific geographic district of the island's southwestern coast.