Lethata fusca is a moth in the Depressariidae family. It was described by Duckworth in 1964. It is found in Brazil (Amazonas). The wingspan is about 25 mm. The forewings are fuscous with a slight purplish hue and the costa is narrowly light rosy ochreous. There is a dark fuscous dot in the fold at the basal third and a white spot at the end of the cell, edged with dark fuscous. An outwardly curved, transverse row of dark fuscous dots is found at the apical four-fifths. The hindwings are whitish ochreous shaded with grey.