Montana is home to 133 documented species of mayflies (Insecta: Ephemeroptera) from 55 genera in 16 families. This study reports on the conservation status, critical habitat, and management needs of 7 mayfly species that are currently listed as Montana species of concern (SOC) and 2 species that are currently listed as potential species of concern (PSOC). Six (67%) of these listed mayflies (Anepeorus rusticus, Analetris eximia, Homoeoneuria alleni, Lachlania saskatchewanensis, Macdunnoa nipawinia, and Raptoheptagenia cruentata) are associated with the sand and gravel benthic habitats of large prairie rivers. Two other mayfly species, Caurinella idahoensis (SOC) and Caudatella edmundsi (PSOC), are associated with small, densely forested streams of the Northern Rocky Mountain Refugium area of the Montana and Idaho border. Distributional data provided for Ametropus neavei (Ametropodidae) and Pseudiron centralis (Pseudironidae) may warrant these species being added to the SOC list. Records of the newest mayfly species recorded in Montana, Cercobrachys cree, are also discussed.