Gal Oya National Park in Sri Lanka was established in 1954 and serves as the main catchment area for Senanayake Samudraya, the largest reservoir in Sri Lanka. Senanayake Samudraya was built under the Gal Oya development project by damming the Gal Oya at Inginiyagala in 1950. An important feature of the Gal Oya National Park is its elephant herd that can be seen throughout the year.
Three important herbs of the Ayurveda medicine, triphala: Terminalia chebula, Terminalia bellirica and Emblica officinalis are amongst the notable flora of the forest. From 1954 to 1965 the park was administrated by the Gal Oya Development Board until the Department of Wildlife Conservation took over administration. The national park is situated 314 km from Colombo.