Abstract The New World eucoiline genus Ganaspidium is revised. Species in this genus are parasitoids of some of the most pestiferous species of leaf-mining Agromyzidae (Diptera), including the notorious Liriomyza trifolii (Burgess). The following new species are described: Ganaspidium didionae, G. eldiablo, G. flemingi, G. kolmaci, and G. konzaensis. Ganaspidium navajoe (Miller), comb. n., is recognized as junior synonym of G. pusillae Weld (syn. n.). Ganaspidium nigrimanus (Kieffer) and G. utilis Beardsley are removed from synonymy, and together with G. hunteri (Crawford), are now in Banacuniculus Buffington. Species of Ganaspidium are recorded from a wide geographic area within North America, and several species appear to be adapted to arid environments. New distribution data, new host records, and a key to known species are provided.