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 8·5-14.0x5.0-6.5 μm); and R. coppinsiana Kantvilas (containing bourgeanic acid and with ascospores 10-19x7-12 μm). The corticolous R. asteriphila Kantvilas lacks lichen substances, contains Sedifolia-grey pigment and has ascospores 10-15x7-10 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.