[3][4] It is found in every mainland South American country except Chile and Uruguay and has been recorded as a vagrant on Trinidad.

[3] The amethyst woodstar was described by the French polymath Georges-Louis Leclerc, Comte de Buffon in 1781 in his Histoire Naturelle des Oiseaux.

[9] The bird was also illustrated in a hand-colored plate engraved by François-Nicolas Martinet in the Planches Enluminées D'Histoire Naturelle which was produced under the supervision of Edme-Louis Daubenton to accompany Buffon's text.

[12] The amethyst woodstar is now placed in the genus Calliphlox that was introduced by the German zoologist Friedrich Boie in 1831.

However, a molecular phylogenetic study of the hummingbird family published in 2014 found that Calliphlox was polyphyletic.

Females have whitish underparts with a few green spangles on the throat and rufous flanks and undertail coverts.

The tail is short and dull green with a black band near the end and pale tips to the feathers.

[20] The amethyst woodstar is found from eastern Colombia through Venezuela and the Guianas into most of Brazil except the main Amazon basin as far south as extreme northeastern Argentina, and from there west and north into Paraguay and through Bolivia, Peru, and Ecuador slightly into southern Colombia.

[20] The amethyst woodstar forages in low bushes and small trees, collecting nectar from a very wide variety of flowering plants.

[20] The amethyst woodstar's breeding season in eastern Brazil spans from November to April; it has not been defined elsewhere.