Cosmopterix lienigiella is a moth of the family Cosmopterigidae.

It is found from Fennoscandia to Spain, the Alps and Greece and from Ireland to Ukraine.

It is the type species of the genus Cosmopterix.

[2] The forewings are light brownish ochreous; costal and dorsal edges white; a fine white longitudinal subcostal line from costa near base to 1/3, another along fold from base to middle, and a short one beneath posterior extremity of this; a somewhat brighter fascia beyond middle, narrowed dorsally, edged with pale golden metallic streaks, posterior interrupted, anterior followed by a variable black spot above middle; a white longitudinal streak from near beyond this to apex.

The larva is rosy-whitish, sometimes with rosy transverse bands; dorsal line darker; head black; 2 broad, with a black mark.