The guqin ([kùtɕʰǐn] ^ⓘ; Chinese: 古琴) is a plucked seven-string Chinese musical instrument. It has been played since ancient times, and has traditionally been favoured by scholars and literati as an instrument of great subtlety and refinement, as highlighted by the quote "a gentleman does not part with his qin or se without good reason," 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". The guqin is not to be confused with the guzheng, another Chinese long stringed instrument also without frets, but with moveable bridges under each string.

Traditionally, the instrument was simply referred to as the "qin" (琴) but by the twentieth 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 (gangqin (钢琴)) and violin (xiaotiqin (小提琴)) are examples of this usage. The prefix "gu-" (古; meaning "ancient") was later added for clarification. Thus, the instrument is called "guqin" today. It can also be called qixian-qin (七絃琴; lit. "seven-stringed qin"). Because Robert Hans van Gulik's book about the qin is called The Lore of the Chinese Lute, the guqin is sometimes inaccurately called a lute. Other incorrect classifications, mainly from music compact discs, include "harp" or "table-harp".^{[citation needed]}

The guqin is 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 has 13 "hui", which represent the different position in one string. Pressing different "hui" produces different sound keys. The qin is also capable of many harmonics, of which 91 are most commonly used and indicated by the dotted positions. By tradition, the qin originally had five strings, which represent gong, shang, jue, zhi, yu in the ancient Chinese music system, but ancient qin-like instruments with only one string or more strings have been found. The modern form has been stabilized to seven strings.

There are more than 3,360 known surviving pieces of guqin music from ancient and imperial periods. On 7 November 2003, UNESCO announced that the Chinese guqin was selected as an Intangible World Cultural Heritage. In 2006, guqin was listed in the List of National Non-material Cultural Heritage in China. In 2010, a Song period guqin was sold for $22 million, making it the most expensive musical instrument ever sold.

Legend has it that the qin, the most revered of all Chinese musical instruments, has a history of about 5,000 years, and that the legendary figures of China's pre-history – Fuxi, Shennong and Huang Di, the "Yellow Emperor" – were involved in its creation. Nearly all qin books and tablature collections published prior to the twentieth century state this as the actual origins of the qin, although this is now viewed as mythology. It is mentioned in Chinese writings dating back nearly 3,000 years, and examples have been found in tombs from about 2,500 years ago. The exact origins of the qin is still a very much continuing subject of debate over the past few decades.

In 1977, a recording of "Flowing Water" (Liu Shui, as performed by Guan Pinghu, one of the best qin players of the 20th century) was chosen to be included in the Voyager Golden Record, a gold-plated LP recording containing music from around the world, which was sent into outer space by NASA on the Voyager 1 and Voyager 2 spacecraft. It is the second-longest excerpt included on the disc. The reason to select a work played on this specific instrument is because the tonal structure of the instrument, its musical scale, is derived from fundamental physical laws related to vibration and overtones, representing the intellectual capacity of human beings on this subject. In 2003, guqin music was proclaimed as one of the Masterpieces of the Oral and Intangible Heritage of Humanity by UNESCO.

As with any other musical tradition, there are differences in ideals and interaction between different people. Therefore, there exist different schools and societies which transmit these different ideas and artistic traditions.

Many qin schools known as qin pai developed over the centuries. Such schools generally formed around areas where qin activity was greatest.