The White-Tailed Goldenthroat (Polytmus guainumbi) is a species of hummingbird in the Trochilidae family. It is found in Argentina, Bolivia, Brazil, Colombia, French Guiana, Guyana, Paraguay, Peru, Suriname, Trinidad and Tobago, and Venezuela. Its natural habitats are dry savanna and subtropical or tropical seasonally wet or flooded lowland grassland.