Cucullia gnaphalii, the cudweed, is a moth of the family Noctuidae.

It is found from most of Europe (except Ireland and most of the Balkan Peninsula)[1] to Turkey, Transcaucasia, Mongolia and Sayan.

Like Cucullia xeranthemi, from which it is distinguished by the more rounded orbicular, not 8-shaped; by the absence of a black shade before outer line in submedian fold, while the black line beyond it is thickened and more conspicuous; the outer line being bent at right angles on the fold, its lower half vertical; above vein 4 a black streak from the reniform stigma, interrupted in the middle; a black streak along middle of inner margin; hindwing brownish, the basal half paler, but not nearly so pale as in xeranthemi.

Larva deep green; dorsal stripe broad, red-brown; spiracles yellow on an interrupted red-brown streak; head green.

The larvae feed on the flowers and leaves of Solidago virgaurea, Solidago canadensis, Artemisia absinthium and Artemisia vulgaris hiding by day under the leaves close to the ground.