The first Carboniferous and ?Permian marine macrofaunas from the Antarctic continent are described from three sites near Mount King, Alexander Island, Antarctic Peninsula. They include bivalves, brachiopods, bryozoans, crinoids, gastropods, a possible monoplacophoran, nautiloids and a possible serpulid or microconchid. Overall the faunas of two localities are Carboniferous in age and compare well with the Levipustula levis Zone of Argentina and eastern Australia, and are of Namurian (Serpukhovian–Bashkirian) age, based mainly on the brachiopod and bryozoan faunas. Less positive brachiopod evidence from a third locality indicates the presence of a linoproductid fauna of possible Carboniferous or Permian (Gzhelian–Artinskian) age, having affinities with the Argentinian Cancrinella fauna. The lithological and structural characteristics of the Mount King beds are comparable to the accretionary complex of the LeMay Group (hitherto of only proven Jurassic–Cretaceous age) of Alexander Island, in which they are provisionally placed. However, the beds may also correlate with the Trinity Peninsula Group (Carboniferous–Triassic) of the northern Antarctic Peninsula. The features of the Mount King beds are consistent with the presence of an accretionery complex related to an island arc in the Late Palaeozoic, but are not necessarily conclusive proof of the presence of such a terrane at that time in what is now Alexander Island.