Stigmella alnetella is a moth of the family Nepticulidae. It is found in all of Europe, except the Balkan Peninsula.
The wingspan is 3.9-4.8 mm. Head orange, collar deep bronze-fuscous. Antennal eyecaps white. Forewings golden brown, becoming lighter golden towards dorsum anteriorly; a bright shining silvery fascia beyond middle, preceded by a dark purplish-fuscous suffusion, apical area beyond this dark purplish fuscous. Hindwings grey.[1]
The larvae feed on Alnus cordata and Alnus glutinosa. They mine the leaves of their host plant. There is usually only one mine in a leaf. Pupation takes place outside of the mine.