The guitar is a musical instrument of the chordophone family. The standard guitar has six strings but four-, seven-, eight-, nine-, ten-, eleven-, twelve-, thirteen- and eighteen-string guitars are also available. The two primary families of guitar types are the electric guitars and the acoustic guitars. The three main types of acoustic guitar are the classical guitar (nylon string guitar, plucked with the fingers), the steel-string flattop guitar, and the archtop guitar.

Guitars are recognized as one of the primary instruments in flamenco, jazz, blues, country, mariachi, rock music, and many forms of pop. The classical guitar (nylon string guitar) can be played as a solo classical instrument, and is well known for its comprehensive fingerpicking technique. Guitars may be played acoustically; the tone is produced by the vibration of the strings which is amplified by the body of the guitar, which acts as a large hollow resonating chamber, or they may rely on an amplifier that can electronically manipulate tone. Such electric guitars were introduced in the 1930s, and they have continued to have a profound influence on popular culture since then.

Traditionally guitars have been constructed of various woods and strung with animal gut, or more recently, with either nylon or steel strings. Guitars are made and repaired by luthiers.