Holcosus undulatus, also known commonly as the barred whiptail, the metallic ameiva, and the rainbow ameiva, is a species of lizard in the family Teiidae. The species occurs in Central America from South Mexico to Costa Rica. There are three recognized subspecies.

 H. undulatus is brown-coloured, with a series of darker zig-zag bars running down the sides, often with light blue and green markings along the sides and underside. It is similar to the Middle American ameiva (H. festivus).

Habitat: H. undulatus lives in litter in open habitats.

Subspecies: The following three subspecies, including the nominotypical subspecies, are recognized as being valid.

• Holcosus undulatus dexter
• Holcosus undulatus miadis
• Holcosus undulatus undulatus

Nota bene: A trinomial authority in parentheses indicates that the subspecies was originally described in a genus other than Holcosus.