A kinglet or crest is a small bird in the family Regulidae. Species in this family were formerly classified with the Old World warblers. "Regulidae" is derived from the Latin word regulus for "petty king" or prince, and refers to the coloured crowns of adult birds. This family has representatives in North America and Eurasia. There are six species in this family; one, the Madeira firecrest, Regulus madeirensis, was only recently split from common firecrest as a separate species. One species, the ruby-crowned kinglet, differs sufficiently in its voice and plumage to be afforded its own genus, Corthylio.
Kinglets are birds of the Nearctic and Palearctic realms, with representatives in temperate North America, Europe and Asia, northernmost Africa, Macaronesia and the Himalayas. They are adapted to conifer forests, although there is a certain amount of adaptability and most species will use other habitats, particularly during migration. In Macaronesia, they are adapted to laurisilva and tree heaths.