The Elachistidae are a family of about 3,200 species of very small moths in the superfamily Gelechioidea. They occur worldwide, with highest diversity in the Holarctic and Australian regions; around 320 species are recorded in North America. 

Adults have wingspans of 4–15 mm, narrow wings with metallic or silky patterns, and are held roof-like at rest. Most are diurnal or crepuscular. Larvae are leaf miners, typically in grasses (Poaceae) or sedges (Cyperaceae), creating long, narrow mines; a few mine in rushes, lilies, or ferns.

The family includes subfamilies such as Elachistinae (with genera Elachista, Cosmiotes, and Perittia) and Parametriotinae. Many species are undescribed, especially in the tropics and southern hemisphere. Recent studies use DNA sequencing and larval mines for species delimitation.