Instruments similar to what we know as the guitar have been popular for at least 5,000 years. The guitar appears to be derived from earlier instruments known in ancient central Asia (Middle East) as the cithara. Instruments very similar to the guitar appear in ancient carvings and statues recovered from the old Iranian Susa. The modern word, guitar, was adopted into English from Spanish guitarra, derived from earlier Greek word kithara. Prospective sources for various names of musical instruments that guitar could be derived from appear to be a combination of two Indo-European roots: guit-, similar to Sanskrit sangeet meaning "music", and -tar a widely attested root meaning "chord" or "string".

The word guitar may also be a Persian loanword to Iberian Arabic. The word qitara is an Arabic name for various members of the lute family that preceded the Western guitar. The name guitarra was introduced into Spanish when such instruments were brought into Iberia by the Moors after the 10th century.

The Spanish vihuela "de mano" appears to be an aberration in the transition of the renaissance guitar to the modern guitar. It had lute-style tuning and a guitar-like body. Its construction had as much in common with the modern guitar as with its contemporary four-course renaissance guitar. The vihuela enjoyed only a short period of popularity, the last surviving publication of music for the instrument appeared in 1576. It is not clear whether it represented a transitional form or was simply a design that combined features of the arabic oud and the European lute. In favor of the latter view, the reshaping of the vihuela into a guitar-like form can be seen as a strategy of differentiating the European lute visually from the Moorish oud. (See the article on the lute for further history.) The Ancient Iranian lute, called tar in Persian also is found in the word guitar. The tar is thousands of years old, and could be found in 2, 3, 5, and 6 string variations.

The earliest extant six string guitar was built in 1779 by Gaetano Vinaccia (1759 - after 1831) in Naples, Italy. The Vinaccia family of luthiers is known for developing the mandolin. This guitar has been examined and does not show tell-tale signs of modifications from a double-course guitar.

Modern dimensions of the classical instrument were established by Antonio de Torres Jurado (1817-1892), working in Seville in the 1850's. Torres and Louise Panormo of London (active 1820s-1840s) were both responsible for demonstrating the superiority of fan strutting over transverse table bracing.

The electric guitar was patented by George Beauchamp in 1936. Beauchamp co-founded Rickenbacher which used the horseshoe-magnet pickup. However, it was Danelectro that first produced electric guitars for the wider public. Danelectro also pioneered tube amp technology.