The classical guitar — (sometimes called the "spanish guitar" or "nylon string guitar") — is a 6-stringed plucked string instrument from the family of instruments called chordophones. The classical guitar is well known for its comprehensive right hand technique, which allows the soloist to perform complex melodic and polyphonic material. (in much the same manner as the piano).

The classical guitar is characterized by:

• its strings — today typically the treble strings (G,B,e) are nylon with the remaining 3 bass strings (E,A,D) being made of nylon fiber wound with metal thread. Though guitar strings are typically made of nylon today, animal gut strings (from the old tradition) are still available)
• the instrumental technique — the individual strings are usually plucked with the fingernails or rarely without nails.
• its historic repertoire, though this is of lesser importance, since any repertoire can be (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, jazz, flamenco, etc.) is 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".

Today the classical guitar is a popular instrument: there exist classical guitar festivals (participant reviews, photos) and summer-schools (documentary video), as well as classical guitar competitions.