The Hiyare Rain Forest is a natural reservoir in the district of Galle, Sri Lanka. This reservoir is a major source of drinking water to the city of Galle. The catchment zone of the reservoir consists of about 600 acres of a rather well preserved lowland rain forest and its conservation is therefore of significance. Further, Mahadola, which is a major stream that enriches the river, originates here.
The floristic composition of the forest consists of important canopy tree species of which 9 endemic species - Hora (Dipterocarpus zeylanicus), Bu - hora, (Dipterocarpus hispidus), Dorana (Dipterocarpus glandulosus), Pini - baru (Hopea jucunda), Kekuna (Canarium zeylanicum), Godapara (Dillenia retusa), Thiniya (Doona congest flora), Uru - honda (Kurrimia ceylanica), Beraliya - dun (Shorea dyeri) - were identified. Among the other life forms 5 endemic bird species, 6 endemic freshwater fish species and 2 endemic amphibian species have been recorded.
The area is a strict forest reserve with a high diversity and endemism of species in the catchment zone.