Astrothelium carassense is a species of corticolous (bark-dwelling), crustose lichen in the family Trypetheliaceae. Found in Brazil, it was formally described as a new species in 2016 by Robert Lücking, Matthew Nelsen, and Marcelo Marcelli. The type specimen was collected by the first author from the Santuário do Caraça (Reserva Particular do Patrimônio Natural, Minas Gerais), at an altitude between 1300and. The lichen has an uneven to bumpy, pale olive-yellow thallus that covers areas of up to 10abbr=onNaNabbr=on in diameter. The pseudostromata are covered with an orange anthraquinone compound. The species epithet carassense refers to the type locality. The characteristics of the lichen that distinguish it from others in genus Astrothelium are its pseudostromatic ascomata, which are, with an orange cover; and the dimensions and form of its ascospores, which are and measure 100–170 by 30–40 μm. Astrothelium purpurascens is somewhat similar in appearance to A. carassense, but it lacks pseudostromatic pigment and has slightly smaller ascospores.