Although Europe is the best-explored continent entomologically, major gaps remain, especially in alpine regions and within taxonomically challenging "dark taxa", such as parasitoid wasps. I describe three new species of Darwin wasps from the Swiss Alps: Diadegma (Nythobia) davidmarquesi sp. nov., D. (Nythobia) mirum sp. nov., and D. (Nythobia) orophilum sp. nov. These species were discovered during a revision of Swiss natural history collections and are diagnosed using morphometric characters, microsculpture, and colour patterns, with comparisons to type material. One species appears to have a wider, possibly boreoalpine distribution, whereas the other two are currently known only from montane to alpine habitats in Switzerland. These findings increase the number of Diadegma species described from the European Alps to 13 and highlight this region as an important reservoir of undescribed Darwin wasp diversity. They further underscore the need for continued integrative taxonomic work, combining museum revision, targeted alpine sampling, and the collection of host data, to more fully document the hidden diversity and biogeographic importance of Europe's alpine insect fauna.