A new genus and species, Nanocthulhu lovecrafti Buffington, is described. This genus is characterized by having a three-pronged structure, referred to as a fuscina, along the dorsal margin of the clypeus; this character is unique in the Hymenoptera. The genus is also characterized by the possession of a corniculum, and the shared possession of this trait with Stentorceps Quinlan suggests these two genera are sister-taxa. A phylogenetic analysis presented here, based on morphology, recovered Stentorceps Nanocthulhu as the sister-group to Trichoplasta Benoit and Rhoptromeris Förster; based on these data, Nanocthulhu is hereby classified in the Trichoplastini. In addition to morphological features, wing interference patterns are described for this new taxon. Though the biology of this unusual wasp is unknown, the head morphology suggests digging is involved at some point in its life history. The possession of a fuscina in both sexes suggests that this structure is involved with emergence, rather than host finding by the female. Errata are provided correcting the holotype information of Stentorceps weedlei Nielsen and Buffington.

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