A new species of the genus Antarctobius Fairmaire (1885) from Islas Malvinas (Falkland Islands) is described and illustrated: A. malvinensis Posadas and Morrone n. sp. (type locality: East Falkland, Mt. Usborne). A key to the species of the genus is presented. A cladistic analysis of the species of Antarctobius, based on 25 characters from the external morphology, genitalia, and body vestiture, is undertaken. The resulting cladogram shows the following sequence: ((A. lacunosus (A. hyadesii, A. vulsus) (A. malvinensis (A. yefacel, A. bidentatus (A. rugirostris (A. abditus (A. germaini, A. falklandicus))))))).