A fretted string instrument of the zither family, typically with 3 or 4 strings, originally and still played as a common folk instrument in the Appalachian region of the eastern USA. The body extends the length of the fingerboard and its fretting is generally diatonic. It is not to be confused with the hammered dulcimer, which is a very different instrument.

Although the Appalachian dulcimer first appeared in the early 19th century among Scottish-Irish immigrant communities in the Appalachian Mountains, the instrument has no known precedent in either Ireland or Scotland. Because of this, and a dearth of written records, the history of the Appalachian dulcimer has been, until fairly recently, largely speculative. However, since 1980, more extensive research has traced the instrument's development through several distinct periods, and likely origins in several similar European instruments such as the Norwegian langeleik.

The Appalachian dulcimer is a plucked box zither and is traditionally constructed of wood. It is made in various sizes but most have a long narrow soundbox, with the 'neck' centred in the soundbox and running the length of the instrument. The soundbox typically has from 2 to 4 soundholes.

At one end of the neck is the headstock, which contains the tuners. At the other end is the tailblock which contains pins or brads for securing the other (loop) end of the strings. Strings are stretched between the end pins and tuners, passing over a bridge (at the tailblock end), and a nut (at the headstock), which determines the sounding length of the strings. In between the nut and the bridge lies the fingerboard, which is fitted with (typically) 12 to 16 metal, diatonically-spaced, frets. Between the end of the fingerboard and the bridge, the neck is carved down to create a scalloped strum hollow where the plectrum, fingers or beater are used to sound the strings.