Occidentalia is a genus of moths of the Crambidae family. It contains only one species, Occidentalia comptulatalis, which is found in North America, where it has been recorded from Alberta, Indiana, Maine, Manitoba, Minnesota, New York, Ontario, Quebec and Saskatchewan. The wingspan is 23-26 mm. The forewings are chocolate brown with dark brown dots in the terminal area. The hindwings are also chocolate brown. Adults are on wing from mid-July to August in one generation per year. The larvae feed on Scirpus acutus, Scirpus americanus and Scirpus validus.