The Tethinidae consist of small gray acalypterate flies found in littoral habitats. About 50 species in some 10 genera are known from all zoogeographic regions.

There are no described fossils known of Tethinidae. However, undetermined specimens have been recorded from the Oligocene/Miocene amber of Chiapas, Mexico by Hurd et al. (1962) and Poinar (1992).