The buff-thighed puffleg (Haplophaedia assimilis) is a species of hummingbird in the "brilliants", tribe Heliantheini in subfamily Lesbiinae.

Adults of both sexes of the nominate subspecies are mostly dark green and have a slightly forked blue-black tail.

[6] The buff-thighed puffleg is thought to seasonally disperse to the lower parts of its elevational range.

In addition to nectar, it feeds on insects that it usually gleans from leaves but occasionally catches by hawking from a perch.

"[6] The IUCN has assessed the buff-thighed puffleg as being of Least Concern, though its population size is not known and is believed to be decreasing.