The golden-breasted puffleg (Eriocnemis mosquera) is a species of hummingbird in the "brilliants", tribe Heliantheini in subfamily Lesbiinae.

Its lower throat and upper breast are coppery bronze and the undertail coverts brownish.

The tail is forked; its central feathers are blue-green and the outer two pairs dark green to blue-black.

The female is slightly smaller and has somewhat greener undertail coverts but is otherwise similar to the male.

[5] The golden-breasted puffleg is suspected to make seasonal elevational movements but has not been documented doing so.

A nest discovered in November in Colombia was a cup made of moss and sticks lined with plant down, placed on the end of a slender branch under a rock overhang.