The long-billed hermit (Phaethornis longirostris) is a bird in the family Trochilidae, the hummingbirds.

[5][6][7] The South American Classification Committee (SACC) of the American Ornithological Society, the International Ornithological Committee (IOC), and the Clements taxonomy assign these four subspecies to the long-billed hermit:[5][4][8] However, BirdLife International's Handbook of the Birds of the World (HBW) treats P. l. baroni as a separate species, "Ecuadorian hermit".

[10] The long-billed hermit is not known to make large-scale movements but is thought to wander short distances.

The nest is a cone-shaped cup made of plant fibers and spider silk suspended from the underside of a drooping leaf.

[10] During the breeding season, male long-billed hermits sing in communal leks of up to 25 birds, and also wiggle their long tails in display.

Competitive lek singing can occupy half of the daylight hours to attract females.

The songs of the three northern subspecies of long-billed hermit are "a continuous series of single, piercing, usually upslurred 'sweeup' notes".