ABSTRACT Introduction During exploration of the central Chilean bryophyte flora over the past 10 years, especially during the wet winter months, a species of Acaulon was collected that did not match any of the known species of the genus. Here, we present our arguments for recognising these plants as a new moss species. Methods The new taxon was compared morphologically with the species of Acaulon currently recognised. In addition, most of the type material of the taxa attributed to this genus was studied. Key results and conclusions Acaulon chilense is described and illustrated as a new moss species from Chile. It is characterised by its reddish coloration, papillose distal laminal cells, costa with homogeneous cells, strongly thickened dorsal cell walls, spores less than 30 μm in diameter, and rhizoautoicous sexuality. The morphological similarities with closely related species are discussed. A distribution map of the new species is provided. This taxon is relatively common, appearing during the wet winter months in the Mediterranean climate areas of the lowlands of central Chile.