The Purple-crowned Fairy is a large hummingbird of humid tropical lowlands. It breeds from southeastern Mexico south to southwestern Ecuador. Both sexes have brilliant emerald-green upperparts, gleaming snow-white underparts and flashy white outer tail feathers. Males of this species have a purple crown, a purple spot at the end of the eyepatch, bordered below with a glittering malar stripe. Females lack the purple and glittering green colors on the head and have a longer tail.