The Scale-backed Antbird (Willisornis poecilonotus) is a species of bird in the Thamnophilidae family, the antbirds. It has often been included in the genus Hylophylax, but is now known to be part of a different clade, leading to its placement in the monotypic genus Willisornis. It was briefly placed in Dichropogon, but this genus is pre-occupied by a genus of asilid flies.
It is found in the Amazon of Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, and Venezuela. Its natural habitat is tropical moist lowland forests. As many other species of antbirds, it regularly follows swarms of army ants.
It addition to being sexually dimorphic, the plumage of the subspecies is highly variable, leading to speculations that it may include more than single species as presently defined. Males of all subspecies, and females of some (but not all) subspecies have white bars on the back, leading to its common name Scale-backed Antbird.