Stigmella assimilella is a moth of the Nepticulidae family. It is found in most of Europe (except Ireland and the Balkan Peninsula), east through Russia to the eastern part of the Palearctic ecozone. Its wingspan is 5–6 millimetres (0.20–0.24 in). The larvae mine the leaves of their host plant, which typically includes species of aspen including Populus alba, Populus canescens and Populus tremula.