Xanthoparmelia subcrustosa is a species of saxicolous (rock-dwelling), foliose lichen in the family Parmeliaceae. Found in South Africa, it was formally described as a new species in 1986 by the American lichenologist Mason Hale. The type specimen was collected by Hale from Cape Province at an elevation of , where he found it growing on granite boulders in karoo vegetation. The thallus of the lichen, which is tightly attached to its rock , is described as "subcrustose" (almost-crust-like), and this trait is referenced in its species epithet. It is pale yellowish green in color and measures broad. Although there are other subcrustose lichen in genus Xanthoparmelia, X. subcrustosa has a unique secondary metabolite (lichen product) complement, containing salazinic, norstictic, connorstictic, and usnic acids.