The guqin (Wades-Giles ku-ch'in; literally "ancient stringed instrument") is the modern name for a seven-string Chinese instrument of the zither family. It's a very quiet instrument, with a range of about four octaves, and its open strings are tuned in the bass register. Its lowest pitch is about two octaves below middle C, or the lowest note on the cello. Sounds are produced by plucking open strings, stopped strings, and harmonics. The use of glissando (sliding tones) gives it a sound reminiscent of a pizzicato cello, fretless double bass or a slide guitar. The qin is also capable of a lot of harmonics, of which 91 are most commonly used and indicated by the dotted positions.

It has traditionally been favoured by scholars and literati as an instrument of great subtlety and refinement, as well as being associated with the ancient Chinese philosopher, Confucius. It is sometimes referred to by the Chinese as "the father of Chinese music" or "the instrument of the sages".

Traditionally, the instrument was simply referred to as qin (Wade-Giles: ch'in) but by the 20th century the term had come to be applied to many other musical instruments as well: the yangqin hammered dulcimer, the huqin family of bowed string instruments, and the Western piano are examples of this usage. The prefix "gu-" (meaning "ancient") was later added for clarification. It can also be called qixianqin (lit. "seven-stringed instrument"). The guqin is not to be confused with the guzheng, another Chinese long zither also without frets, but with moveable bridges under each string. The guqin is sometimes inaccurately called a 'lute', 'harp' or 'table-harp'.

In 1977, a recording of "Flowing Water" (Liu Shui, as performed by Guan Pinghu) was chosen to be included as the longest excerpt on the Voyager Golden Record, a gold-plated LP recording containing music from around the world and sent into outer space. The reason why this specific instrument was included is because of its tonal structure of the instrument. Its musical scale is derived from fundamental laws of vibration and overtone, so representing the capacity of its makers. In 2003, Guqin music was proclaimed as one of the Masterpieces of the Oral and Intangible Heritage of Humanity by UNESCO.