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 . 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.