The long-billed starthroat (Heliomaster longirostris) is a species of hummingbird in the "mountain gems", tribe Lampornithini in subfamily Trochilinae. It is found in Mexico, Central America, Trinidad, and all but the four southernmost countries of South America.
Taxonomy and systematics
At one time the long-billed starthroat was placed in genus Anthoscenus but since the mid-1900s has had its current placement in Heliomaster. It has three subspecies, the nominate H. l. longirostris, H. l. pallidicepts, and H. l. albicrissa.
Males of the nominate subspecies have a glittering blue to greenish blue crown; the rest of its upperparts are dark bronzy green with the exception of a white stripe down the center of the rump. The face is black below the crown and has a white malar stripe below the black. Its tail is rather short and square-tipped. The feathers are bronzy green near the body and black away from it, and the outer two or three pairs have white tips. The chin is black, the gorget dark metallic purple, the breast gray with bronzy green sides, and the lower breast and belly dull white. The undertail coverts are gray with white edges. Nominate females are very similar but the blue of the crown is much reduced or absent and the gorget is narrower and dusky gray.