The Grass-green Tanager (Chlorornis riefferii) is a small passerine bird, one of the tanager family. It is the only member of the genus Chloronis.

The Grass-green Tanager is 20 cm in length and weighs 53g. It lives in and around subtropical and temperate forests in the Andes of Colombia, Ecuador, Bolivia and Peru at elevations of 1500-3350 m. It is seen in pairs or in groups of 3-6 individuals. It forages mostly on upper half of short trees and eats fruits and insects. It is known to perch almost horizontally. Its nest is made of mosses and ferns, and its eggs are gray with light purple/grey dots.