The cosmopolitan genus Nephus Mulsant is traditionally divided into several subgenera of uncertain status. Its nominotypic subgenus is known to occur mainly in Palaearctic, Afrotropic and Oriental Realms, with a single species recorded from North America. From the Australo-Pacific region only three species of Nephus were recorded so far, two from New Guinea and one from Fiji, however, none of them was assigned to any subgenus. The genus is recorded from the Australia for the first time, based on a revision of the type material of Scymnus compositus Lea, 1902 (= Nephus compositus (Lea) comb. nov.) and a new species, Nephus septentrionalis sp. nov. from Northern Territory and Queensland. Detailed illustrations, descriptions and distribution map are provided.