The Coelopidae or kelp flies are a family of Acalyptratae flies (order Diptera), they are sometimes also called seaweed flies, though both terms are used for a number of seashore Diptera. Fewer than 40 species occur worldwide. The family is found in temperate areas, with species occurring in the southern Afrotropical, Holarctic, and Australasian (which has the most species) regions.