Five new species of Rimularia, all endemic to Tasmania, are described, discussed and illustrated: Four species are saxicolous: R. albotessellata Kantvilas (containing pannarin): R. aspicilioides Kantvilas (containing 2′-O–methylperlatolic acid and with apothecia with a thalline margin); R. circumgrisea Kantvilas (containing norstictic acid, and with ascospores 8·5–14·0×5·0–6·5 µm); and R. coppinsiana Kantvilas (containing bourgeanic acid and with ascospores 10–19×7–12 µm). The corticolous R. asteriphila Kantvilas lacks lichen substances, contains Sedifolia-grey pigment and has ascospores 10–15×7–10 µm. The widespread R. psephota (Tuck.) Hertel & Rambold, with which several of the new taxa are compared, is also described, based on Tasmanian collections. Several chemical compounds, including bourgeanic acid, pannarin and 2′–O–methylperlatolic acid, are recorded for the genus for the first time. A key to the 12 species currently recorded for Tasmania is presented.
