[1] The name of the genus is derived from the Latin regulus, a diminutive of rex, "a king",[2] and refers to the characteristic orange or yellow crests of adult kinglets.

A phylogenetic analysis based on the cytochrome b gene showed that the Madeiran form is distinct at the species level from the firecrest nominate subspecies R. i. ignicapillus.

[4] The golden-crowned kinglet is similar in appearance to the common firecrest and has been considered to be its New World equivalent, but it is actually closer to the goldcrest.

[3] Goldcrests from the Canary Islands are particularly distinctive having a black forehead, pink-buff underparts and a darker closed wing,[5] and have been sometimes treated either as a subspecies of the common firecrest or as a different Regulus species altogether.

[6] They were sometimes called the Tenerife goldcrest, no matter which of the islands they lived on; however, a 2006 study of the vocalisations of these birds indicate that they actually comprise two subspecies of the Goldcrest that are separable on voice; R. r. teneriffae occurring on Tenerife and the newly described subspecies, R. r. ellenthalerae, occurring on the smaller islands of La Palma and El Hierro.