Astrothelium corallinum is a species of corticolous (bark-dwelling), crustose lichen in the family Trypetheliaceae.

The type specimen was collected from Rain Mountain, southeast of the village in Paruima Mission (Upper Mazaruni District) at an altitude of 500 m (1,600 ft); here, it was found growing on the smooth bark of trees in a rainforest.

The lichen has a smooth, somewhat shiny thallus that covers areas of up to 8 cm (3.1 in) in diameter; the entire thallus is surrounded by a thin (0.3 mm) black line that is the prothallus.

The whitish parts of the pseudostromata will fluoresce yellow when lit with a long-wavelength UV light; this is due to the presence of lichexanthone, a lichen product.

The thallus, however, does not contain lichexanthone, which distinguishes it from the similar species A. ochroleucoides.