The family Pseudopomyzidae is revised. Morphological characters and multiple genes are used to assess relationships among the families of Nerioidea, concluding that the family Pseudopomyzidae as currently defined is paraphyletic with respect to Cypselosomatidae and that the family Cypselosomatidae should therefore be redefined to include the Pseudopomyzidae. The current subgeneric classification of the large genus Pseudopomyza is rejected in favour of dividing the genus into four species groups: the antipoda species group, the atrimana species group, the collessi species group and the flavitarsis species group. The Pseudopomyza antipoda species group includes P. antipoda (Harrison) and P. brevis (Harrison), both from the New Zealand Subantarctic Islands. The Pseudopomyza atrimana species group includes P. aristata (Harrison) (New Zealand), P. atrimana (Meigen) (Palaearctic), P. brevicaudata (Harrsion) (New Zealand), P. brevifacies (Papp) (Oriental and Palaearctic) and the Neotropical clade formerly treated as the subgenus Rhinopomyzella. The Neotropical clade of the Pseudopomyza atrimana species group, shown here to be the sister group to P. atrimana, includes P. albimana (Hennig), P. nigrimana (Hennig) and fifteen new species (P. adunca, P. ampliata, P. angustifrons, P. binaevia, P. brunneicacumen, P. cordata, P. cyathiformis, P. flavicacumen, P. gambiformis, P. inflexa, P. machaera, P. parabinaevia, P. proboscis, P. prolata, P. simulatrix). The Pseudopomyza collessi species group includes P. collessi McAlpine (Australia). The Pseudopomyza flavitarsis species group includes the two species formerly treated as the subgenus Apops (P. flavitarsis (Harrison) (New Zealand) and P. arenae McAlpine (Australia, Tasmania)) and three new species (P. chilensis (Chile), P. medianentis (Australia, Western Australia) and P. nigritarsis (New Zealand)). Natural Sciences and Engineering Research Council of Canada; Queen Elizabeth II Graduate Scholarship in Science and Technology; Ontario Graduate Scholarships; University of Guelph Scholarships and Awards; Ken Stead. 2024-05-05