We describe a new species of Rhacophorus from lowland forests in southern Vietnam. The new species is most similar to Rhacophorus kio, but differs from this and all other Rhacophorus from Southeast Asia by a combination of its large body size (males 72.3–85.5 mm; females 89.4–90.7 mm snout–vent length); green dorsum; white venter; black patch at axilla; bluish-green posterior surface of thighs with pale yellow marbling; low, single-lobed supracoloacal dermal ridge, and white sclera. In contrast to the widely distributed R. kio, the new species is known only from two fragments of disturbed, low-elevation forest approximately 30 km apart in a highly modified agricultural landscape. The continued survival of the new species is threatened by ongoing habitat loss and degradation.