The Purple-throated Mountain-gem Lampornis calolaemus is a medium-sized species of hummingbird (Trochilidae), with a straight, dark bill. It occurs in the montane cloud forests of Nicaragua, Costa Rica, and Panama. Both males and females of this species are characterized by stunning iridescent green contour feathers, which cover most of their bodies, and white post-ocolar stripes. This species is sexually dimporphic in plumage. The males are primarily green, with a purple gorget. The upperparts of the female are green, but the underparts are pale rufous, and the female lacks a gorget. Purple-throated Mountain-gems are territorial nectarivores, supplementing their diets with occasional insect prey. This species breeds primarily during the rainy season, from October to April, and nests in the understory. Males make their presence known with repeated short bursts of insect-like trills.