The Black Hills, straddling the border between southwestern South Dakota and northeastern Wyoming, represent an ecological "island" of mountainous terrain in the midst of the Great Plains. Streams, rivers, lakes, and ponds are abundant, yet the aquatic insect fauna inhabiting those ecosystems has not previously been compiled in a single document. This work demonstrates that the known fauna of 95 families, 335 genera, and 447 species-level aquatic insect taxa has a curious mix of eastern, western, northern, and southern biogeographic affinities, yet many significant data gaps remain, and this work can only represent a starting point. The Black Hills beckon more curious naturalists to come and add to our knowledge.