On 17 January 2013, we discovered a nest of White-sided Hillstar (Oreotrochilus leucopleurus) in a sheltered part of a cliff-face, c. 6 m from its base, at Los Farallones, V Region, Chile. The female was obviously incubating eggs, although these could not be seen (but there was no evidence of young being present). The nest was a bulky, slightly funnel-shaped structure positioned in a S-facing fissure in the rock and below an overhang, affording maximum protection from the elements, and also suggesting that the nest was constructed to fill the available space. We estimated the nest to be c. 85 mm deep and 65 mm in external diameter, and it was constructed of seed-down, Puya wool, dry grass, moss, feathers and other unidentified plant material, as well as some blue twine, bound partially with cobwebs. This observation (unsurprisingly) extends the known breeding season of the species. Its nest is (also unsurprisingly) similar to those of other Oreotrochilus hummingbirds that have been subject to more detailed description.