Aseptis fumosa is a moth of the family Noctuidae first described by Augustus Radcliffe Grote in 1879.

It occurs in a variety of diverse habitats including coast chaparral, dry conifer forest, and shrub steppe.

The forewings are uniform smoky dark blackish brown with brown filling of the antemedial and postmedial lines that is most evident as dots on the costa.

The male hindwing is pearly gray distal to the spot that accentuates the vein asymmetry.

The larvae feed on Purshia (including Purshia tridentata), Cercocarpus and Ceanothus (including Ceanothus integerrimus) species, as well as Adenostoma fasciculatum.