songbird family, order Passeriformes, consisting of the Old World warblers, almost 300 species of small, dull-coloured active birds found in a variety of habitats.

Members range in size from 9 to 26 centimetres (3.5 to 10 inches) long. They have thin bills; long nostrils with a covering flap; medium, rounded wings; and weak legs and feet. Old World warblers have 10 primary feathers in each wing, instead of nine, as in the New World wood warblers (family Parulidae). In woods, brushlands, and marshes these birds search for insects. They are good singers, though not equal to thrushes. Sylvia includes many common European birds, such as the garden warbler (S. borin), whitethroat (S. communis), and blackcap (S. atricapilla).

The family is sometimes divided into the following subfamilies: warblers proper (Sylviinae), gnatcatchers (Polioptilinae), kinglets (Regulinae), and wren-warblers (Malurinae). Some authorities list the subfamily Sylviinae in the family of Old World flycatchers (Muscicapidae). In other classifications, as here, these subfamilies are raised to family rank.

The Sylviidae belongs to the songbird suborder (Passeres).