The harp guitar (or "harp-guitar") is a stringed instrument with a history of well over two centuries. While there are several unrelated historical stringed instruments that have appropriated the name “harp-guitar” over the centuries, the term today is understood as the accepted vernacular to refer to a particular family of instruments defined as "A guitar, in any of its accepted forms, with any number of additional unstopped strings that can accommodate individual plucking." Additionally, in reference to these instruments, the word "harp" is now a specific reference to the unstopped open strings, and is not specifically a reference to the tone, pitch range, volume, silhouette similarity, construction, floor-standing ability, nor any other alleged "harp-like" properties. To qualify in this category, an instrument must have at least one unfretted string lying off the main fretboard. Further, the unfretted strings can be, and typically are, played as an open string.
This family consists of an almost limitless variety of different instrument configurations. Most readily identified are American harp guitars with either hollow arms, double necks or harp-like frames for supporting extra bass strings, and European bass guitars (or kontragitarres). Other harp guitars feature treble or mid-range floating strings, or various combinations of multiple floating string banks along with a standard guitar neck.