Hydrophylax gracilis, also known as Gravenhorst's frog, Gravenhorst's golden-backed frog, and Sri Lanka wood frog, is a species of frog in the family Ranidae. It is endemic to Sri Lanka. Hydrophylax gracilis occurs in marshes, agricultural land, grassland, and bush forests at elevations below 600 m. Adult frogs are semi-arboreal and semi-aquatic, whereas the tadpoles live in stagnant waters. H. gracilis is a common species that can be threatened by loss of its wetland habitats through wetland reclamation, urbanization, and aquatic agrochemical pollution. However, it is present in many protected areas.