Caloptilia robustella (commonly known as new oak slender)[1] is a moth of the family Gracillariidae. It is known from all of Europe, except the Balkan Peninsula.
The wingspan is 10-. To differentiate this species from Caloptilia alchimiella requires microscopic examination of the genitalia. There are multiple generations per year, with adults on wing between April and November.[2]
The larvae feed on Fagus sylvatica and Quercus robur. They mine the leaves of their host plant.[3]