Etheostoma akatulo, the Bluemask Darter, is described from upper Caney Fork River System of the middle Cumberland River drainage, Tennessee. It is presently known from four tributaries of Great Falls Reservoir on the eastern Highland Rim and is listed as federally endangered. The new species differs from other species of the subgenus Doration by having fully scaled cheeks, complete lateral line, breeding males with bright blue pigment completely covering the lower face, and breeding males with soft dorsal and anal fins lacking orange and blue pigment. Specimens are compared with nominate E. stigmaeum from four drainages and E. jessiae. Etheostoma akatulo typically occurs over sand and gravel substrates downstream of riffles, in moderate runs, or along margins of pools. It inhabits a 37-km reach of Collins River but is found in reaches of 4.3 km or less in Rocky River, Cane Creek, and Caney Fork River. Threats to the species include gravel dredging, pesticides, siltation, and acid mine drainage.