Diarsia dahlii, the barred chestnut, is a moth of the family Noctuidae.

It is found in Europe, through the Palearctic east to the Kamchatka Peninsula, northern China and Japan.

Forewing reddish brown with an ochreous tint in the male, darker, purplish brown in female; lines plain in the paler males; stigmata of the ground colour, the reniform with the lower lobe dark, the upper sometimes ochreous; claviform with a black dot at the tip; a distinct dark median shade; in the female the submarginal line is pale; hindwing dull fuscous, the fringe pinkish.

The larva varies in the colour of the back through various shades of ochreous and brown to dark reddish brown, and this is always in strong contrast with the colour of the lower parts; the lines are pale, and the outer ones on the back are edged with black dashes; spots and spiracles black; head pale brown.

The larvae feed on Betula, Vaccinium myrtillus, Rumex and Plantago.