The guitar zither (or harp zither) is a musical instrument consisting of a soundbox, with two sets of unstopped strings. One set of strings is tuned to the diatonic scale and the other set is tuned to make the various chords in the key of the diatonic strings.

The guitar zither came into use in the 19th Century, and was widely mass-produced in the United States and in Germany.

A form of psaltery, the guitar zither is closely related to the Autoharp. It differs from the concert zither in not having a fret board.

The name guitar zither is apparently derived from its sound, as the concert zither is more closely related to the guitar, in performance method, and in physical form, than is the guitar zither. A closely related instrument, the mandolin zither, has doubled strings, for a more mandolin-like sound.