The new genus and species, Nanophemera myanmarensis McCafferty and Santiago-Blay, is described from an adult mayfly of the extinct family Australiphemeridae imbedded in Burmese amber, probably of Upper Cretaceous age. Nanophemera is the fifth genus known in the Australiphemeridae (a Pangaean, Cretaceous family), which is hypothesized to represent a primitive group of small-sized, tusked, burrowing mayflies (Scapphodonta), possibly closely related to the extant family Potamanthidae. Nanophemera is among the smallest known burrowing mayflies at slightly over four millimeters in length, and it differs from related genera by details of its cubital and anal venation systems in the forewings. The newly described fossil is the second mayfly discovered from Burmese amber.