The zither is a musical string instrument, most commonly found in Slovenia, Austria, Hungary, northwestern Croatia, the southern regions of Germany, alpine Europe and East Asian cultures, including China. The term "citre" is also used more broadly, to describe the entire family of stringed instruments in which the strings do not extend beyond the sounding box, including the hammered dulcimer, psaltery, Appalachian dulcimer, guqin, guzheng (Chinese zither), koto, gusli, kantele, gayageum, đàn tranh, kanun, autoharp, santoor, yangqin, piano, harpsichord, santur, swarmandal, and others. Modern electric zithers exist, as well as a wide variation of experimental zithers like the Kitaras of Harry Partch, the Shruti Stick and the Moodswinger. It is played by strumming or plucking the strings like a guitar.

The word "citara" is derived from the Greek word kithara, an instrument from classical times used in Ancient Greece and later throughout the Roman Empire and in the Arab world (Arabic قيثارة); the word "guitar" derives from "qithara" as well.