The new species Ramboldia blastidiata Kantvilas & Elix, from Tasmania and mainland Australia is described, and the new combination, R. elabens (Fr.) Kantvilas & Elix is proposed. The South American R. petraeoides var. concava (Müll. Arg.) Fryday is considered a synonym of R. petraeoides (Nyl. ex C. Bab. & Mitt.) Kantvilas & Elix s. str., and R. crassithallina Kalb and R. sorediata Kalb, both previously considered endemic to Western Australia, are recorded from Tasmania for the first time. A key to the 11 species of Ramboldia is presented.