Elachista unifasciella is a moth of the family Elachistidae found in Asia and Europe.
The wingspan is . Adults are on wing from June to July in one generation per year.
The larvae feed on Avenula pubescens, false-brome (Brachypodium sylvaticum), cock's-foot (Dactylis glomerata), creeping soft grass (Holcus mollis) and wood millet (Milium effusum). They mine the leaves of their host plant.
It is found from Sweden to the Pyrenees, Italy and Greece and from Great Britain to Russia and Turkey.