Coenogonium australiense is a species of corticolous (bark-dwelling), crustose lichen in the family Coenogoniaceae. Found in Australia, it was formally described as a new species in 2018 by lichenologists Gintaras Kantvilas and Robert Lücking. The type specimen was collected by the first author near Little Fisher River (Tasmania) at an altitude of 880m (2,890feet), where it was found in a rainforest growing on Nothofagus cunninghamii. The species epithet australiense refers to its geographical distribution. In addition to Tasmania, the lichen has also been documented from New South Wales and Kangaroo Island. In the latter location it was found in remnant stands of coniferous woodland, where it was growing on the bark of old, fissured Callitris trunks.
The thallus of Coenogonium australiense is crustose and varies in thickness, forming irregular patches on . The cells are somewhat spherical to ellipsoid in shape and can be found as single cells or short chains. The apothecia, or fruiting bodies, are and have an orange-pink with a cream-colored or translucent margin. The is colorless and 60–120 μm thick, while the is 40–80 μm thick and colorless or pale yellowish-brown. The hymenium is 60–80 μm thick and contains asci and paraphyses. Ascospores are typically and arranged obliquely in the ascus, measuring 10–14 by 3–4.5 μm. are visible on the upper thallus surface as tiny pale swellings; the are ellipsoid and measure 3–5 by 1–3 μm.