© 2015 American Museum of Natural History. A new genus of oonopid spider, Sicariomorpha Ott and Harvey, is named for the type and only known species, Gamasomorpha maschwitzi Wunderlich from Malaysia. The most striking feature of the spider is the eyes, which are arranged in two widely separated triads. Besides taxonomic description, we summarize the biology of Sicarimorpha maschwitzi, which is a kleptoparasite of the Southeast Asian army ant Leptogenys distinguenda (Emery) and one among only few well-studied myrmecophilous spiders. Its morphology, behavior and life history seem to be well adapted for the life with its predatory army ant host.