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.