Cosmia diffinis, the white-spotted pinion, is a moth of the family Noctuidae The species was first described by Carl Linnaeus in 1767.

To the south, it is found down to Spain, Italy, Russia, northern Greece and Bulgaria.

Forewing rich redbrown on a pinkish grey ground; distinguished from the other [Cosmia] species by the lines starting from broad white costal blotches, not narrow streaks; the hindwing paler, more olive brown, than in affinis; — ab.

(47 e) has the pinkish ground colour predominant, the shading pale golden brown, the hindwing sometimes yellowish with dark outline and submarginal shade; on the contrary the ab.

(47 e) has the deep purple tints intensified and darker, the insect being slightly smaller.