The Green-Tailed Goldenthroat (Polytmus theresiae) is a species of hummingbird in the Trochilidae family. It is found in Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, and Venezuela. Its natural habitats are subtropical or tropical moist lowland forests, subtropical or tropical seasonally wet or flooded lowland grassland, and heavily degraded former forest.