The dark dagger (Acronicta tridens) is a moth of the family Noctuidae.

This species has grey forewings marked with bold black "daggers".

Adults of this species are extremely similar to the grey dagger (Acronicta psi).

Despite the common name, the dark dagger is usually the paler of the two species and the white hindwings of the male are usually diagnostic.

This species flies at night in June and July[a] and is attracted to light and sometimes to sugar.