Resapamea mammuthus is a moth in the Noctuidae family. It only known only from the type locality at Old Crow, Yukon Territory. The length of the forewings is 21.5 mm for males. The forewings are a mixture of tan, orange-tan, gray-tan, light-gray, brown-gray, and gray scales, appearing medium-dark orange tan, grayer near anterior and posterior margins and darker gray-brown in the terminal area. The hindwings are light gray tan with gray suffusion, very faint postmedial line, marginal band, terminal line, veins, andchevron-shaped discal spot.