This paper documents the previously undescribed terrestrial fauna (mites, nematodes, tardigrades) and flora (liverworts, mosses and lichens) of Marion Nunataks, Charcot Island (69°45'S 075°15'W). Species diversity in all groups is low relative to other Maritime Antarctic sites, probably a twin function of very limited ice-free terrain and extreme isolation. The fauna and flora are wholly immigrant and, with the exceptions of two lichens (Psilolechia lucida and Umbilicaria aff. thamnodes), clearly derived from the Maritime Antarctic. The fauna is unique for the Maritime Antarctic in that it appears to contain neither predatory arthropods nor Collembola (springtails), which are otherwise ubiquitous and important members of the terrestrial fauna of the zone. The flora includes exceptional development of three mosses that are encountered only rarely at latitudes south of c. 65°S, Brachythecium austrosalebrosum, Dicranoweisia crispula and Polytrichum piliferum. The southern limit for several mosses and lichens has been extended. This small and isolated site is extremely vulnerable to accidental human-mediated introduction of both native Antarctic and alien biota.