The long-billed starthroat (Heliomaster longirostris) is a species of hummingbird in the "mountain gems", tribe Lampornithini in subfamily Trochilinae.

Both sexes of all subspecies have a long, almost straight, black bill and a small white spot behind the eye.

Nominate females are very similar but the blue of the crown is much reduced or absent and the gorget is narrower and dusky gray.

[6] Subspecies H. l. pallidicepts has a more greenish blue crown than the nominate and the sides of the breast are golden bronze.

[6] Subspecies H. l. pallidicepts of long-billed starthroat is the northernmost; it is found from southern Mexico through Belize, Guatemala, Honduras, and El Salvador into Nicaragua.

[6] The long-billed starthroat feeds on nectar, especially at the flowers of large trees but also those of vines, shrubs, and Heliconia.

The nest is a shallow cup made of plant down, moss, and liverworts cemented with spider silk and covered with lichen.

The long-billed starthroat's calls include "a rich liquid 'tseep' or 'tsew'" and "sqeaky twitters"; the latter is made during chases.

It is "evidently able to tolerate much disturbance, and perhaps even favoured by deforestation, as long as scattered trees and groves remain.