The Platystomatidae, commonly known as signal flies, are a family of acalyptrate flies characterised by their often boldly patterned wings and distinctive display behaviour.

Members of the family are medium-sized flies with a robust body and a relatively broad head bearing well-developed compound eyes. Antennae are short to moderate in length, typically with an aristate third segment. The thorax and abdomen are variably coloured, frequently marked with contrasting dark and pale patterning.

The wings are a defining feature. Many species possess conspicuous bands, spots, or reticulate markings, which are actively displayed by wing-waving or wing-flicking movements. Wing venation is well developed, with a closed discal cell and clearly defined cross-veins, aiding separation from superficially similar picture-winged flies.

Larvae are saprophagous, developing in decaying organic material such as rotting vegetation, leaf litter, decomposing wood, or dung. Adults are commonly encountered in woodland margins, scrub, hedgerows, and grassland, where they feed on nectar, honeydew, or other surface liquids associated with decaying matter.

Platystomatidae have a worldwide distribution, with highest species richness in tropical and subtropical regions, though a smaller but characteristic fauna occurs in temperate zones. In the Palearctic region, genera such as Rivellia are among the most frequently recorded.

Within Diptera, Platystomatidae are noted for their behavioural displays and visually striking appearance, making them one of the more recognisable families within the Tephritoidea.