The harp guitar is a guitar-based stringed instrument generally defined as a "guitar, in any of its accepted forms, with any number of additional unstopped strings that can accommodate individual plucking." The word "harp" is used in reference to its harp-like unstopped open strings. A harp guitar must have at least one unfretted string lying off the main fretboard, typically played as an open string.

The harp is a stringed musical instrument that has individual strings running at an angle to its soundboard; the strings are plucked with the fingers. Harps can be made and played in various ways, standing or sitting, and in orchestras or concerts. Its most common form is triangular in shape and made of wood. Some have multiple rows of strings and pedal attachments.