Mallochianamyia Santos-Neto was proposed as a replacement name for Gayomyia Malloch, 1933 (preoccupied by Gayomyia Banks, 1913), an unplaced genus of acalyptrate Diptera from Chile and Argentina. The genus comprises 12 species: M. cladostyla sp. n.; M. fenestrata sp. n.; M. flavitibia sp. n.; M. furcata sp. n.; M. gallina sp. n.; M. latigena sp. n.; M. magnipalpis sp. n.; M. nigrohalterata (Malloch) comb. n.; M. penai sp. n.; M. setosa sp. n.; M. truncata sp. n.; M. vexans sp. n. All new species are illustrated and a key to species of Mallochianamyia is provided. The monophyly of the genus is supported by three characters of the male and female genitalia. Mallochianamyia is most closely related to the New World genera Paraleucopis Malloch and Schizostomyia Malloch and an undescribed Australian genus. The group cannot be placed in any established family as currently defined, although there are affinities to some families in the Asteioinea sensu J. F. McAlpine (1989). Research on the morphology and relationships of genera related to Mallochianamyia is required to clarify the familial status of the group.