The grey chi is a moth of the family Noctuidae. The species was first described by Carl Linnaeus in his 1758 10th edition of Systema Naturae. It is distributed throughout Europe, although it is not present in southern Spain and Greece, as well as northern Fennoscandia. It is also found across the Palearctic including Central Asia, to the Russian Far East but not in Japan.

In the 10th edition of Systema Naturae, Carl Linnaeus classified the arthropods, including insects, arachnids and crustaceans, among his class "Insecta". Butterflies and moths were brought together under the name Lepidoptera. Linnaeus divided the group into three genera – Papilio, Sphinx and Phalaena. The first two, together with the seven subdivisions of the third, are now used as the basis for nine superfamily names: Papilionoidea, Sphingoidea, Bombycoidea, Noctuoidea, Geometroidea, Tortricoidea, Pyraloidea, Tineoidea and Alucitoidea.