Hahncappsia mellinialis is a moth in the Crambidae family. It was described by Druce in 1899. It is found in Colorado, Arizona, New Mexico, Mexico and Guatemala. The wingspan is 28–32 mm for males and 27–31 mm for females. The forewings are straw-yellow, irrorated with buff. The hindwings are somewhat paler. Adults have been recorded on wing from July to September.