The classical guitar, also known as the "nylon string guitar" — is a plucked string instrument from the family of instruments called chordophones. It typically has 6 nylon strings (the 3 bass-strings additionally being wound with a thin metal thread). The classical guitar is well known for its comprehensive fingerpicking technique, which enables the solo rendition of melody, multi-voiced harmony and polyphony (in much the same manner as the piano can).

The classical guitar is characterized by:

• its strings — today primarily nylon; the bass-strings additionally being wound with a thin metal thread (traditionally they were made of gut - gut strings are still available today)
• the instrumental technique — the individual strings are usually plucked with the fingers or the fingernails — plectra are rarely used
• its historic repertoire, though this is of lesser importance, since any repertoire can (and is) played on the classical guitar (additionally: classical guitarists are known to borrow from the repertoires of a wide variety of instruments)
• its shape, construction and material — modern classical guitar shape, or historic classical guitar shapes (e.g. early romantic guitars from France and Italy). A guitar family tree can be identified. (The flamenco guitar is derived from the modern classical, but has differences in material, construction and sound.)

The name classical guitar does not mean that only classical repertoire is performed on it, although classical music is a part of the instrument's core repertoire (due to the guitar's long history); instead all kinds of music (folk, alternative, jazz, flamenco, etc.) can be and are performed on it.

The term modern classical guitar is sometimes used to distinguish the classical guitar from older forms of guitar, that are in their broadest sense also called classical, or more descriptively: early guitars. Examples of early guitars include the 6-string early romantic guitar (ca. 1790 - 1880), and the earlier baroque guitars with 5 courses.

Today's modern classical guitar is regarded as having been established from the late designs of the nineteenth century Spanish luthier Antonio Torres Jurado. Hence the modern classical guitar is sometimes called the "Spanish guitar".

The modern classical guitar is usually played in a seated position, with the instrument resting on the left lap - the left foot is usually placed on a footstool. Alternatively - if a footstool is not used - a guitar support can be placed between the guitar and the left lap (the support usually attaches to the instrument's side with suction cups). (There are of course exceptions, with some performers choosing to hold the instrument another way.)