The mayfly fauna (Insecta: Ephemeroptera) in Iraq is very poorly known, with only four taxonomic studies from northern Iraq, two of them conducted more than 30 years ago. There are no published keys or guides for larval identification for that fauna. We conducted the fifth study in the Kurdistan Region of northern Iraq and created the first hierarchical checklist and larval key to the families, subfamilies, genera, and subgenera. The checklist and key were produced after reviewing the diagnostic morphological features for each of these taxonomic levels using references from Europe, West Asia, North Africa, the Caucasus, the Trans-Caucasus, and the Middle East. Finally, an illustrated identification key for nine families, nine subfamilies, 19 genera, and 13 subgenera is provided with illustrations prepared from specimens collected during this study. Based on the findings of this research, at least 24 species of mayflies inhabit the region.