© 2021 The Royal Society of New Zealand.The first author collected lichens in the austral summer of 2017 from James Ross Island, located in the North-East region of the Antarctic Peninsula, which is one of the lichen-rich islands in Antarctica, with around 60 species reported previously. In this project, the lichen biodiversity of the island is studied by using molecular techniques in addition to morphological characters. Our results show that the lichen biodiversity of Antarctica is not well known, as many undescribed or unreported species are still present. One of the undescribed species is Leptogium pirireisii, a cyanolichen with Nostoc photobiont, a nitrogen fixer. In the nuITS phylogenetic tree, L. pirireisii clustered, with high support, with the species L. antarcticum, L. furfuraceum, L. marcellii, L. pseudofurfuraceum, L. puberulum and L. tectum, which are all characterised by the presence of hairs, while these are absent in the new species. We also confirmed the occurrence of L. antarcticum on James Ross Island based on molecular data and further generated nuITS sequences of L. puberulum.