The Old World silversides are a family, Atherinidae, of fish in the order Atheriniformes. Atherinidae are abundant and considered bony fish (teleost) that are widespread globally, living in rivers, estuaries, and coastal waters. They occur worldwide in tropical and temperate waters. About two-thirds of the species are marine, and the remainder live in fresh water. The 74 species are in 13 genera. The genus Craterocephalus is the most diverse with 25 species. Four genera are monotypic.

Silversides are relatively small with most being less than 20 cm (7.9 in) in length, with several not attaining lengths of more than 5 cm (2.0 in). The body is generally elongated. Distinctive characters include two dorsal fins widely separated, with the first consisting of flexible spines and the second having one spine followed by soft rays, while the anal fin has one spine on the leading edge followed by soft rays. The pectoral fins tend to be high, and there is no lateral line. On the flanks is a broad, silvery band. The scales are relatively large.

They feed on zooplankton. Some species, such as the hardyhead silverside, Atherinomorus lacunosus, are commercially fished.

The family Atherinopsidae (Neotropical silversides) is closely related, while the genus Atherion has been given family status in the Atherionidae by some authorities.