In which country is the guitar believed to have originated?

The guitar is a plucked or strummed stringed musical instrument that probably originated in Spain early in the 16th century, deriving from the 'guitarra latina', a late-medieval instrument with a waisted body and four strings. The early guitar was narrower and deeper than the modern guitar, with a less pronounced waist. It was closely related to the vihuela, the guitar-shaped instrument played in Spain in place of the lute.

The guitar originally had four courses of strings, three double, the top course single, that ran from a violin-like pegbox to a tension bridge glued to the soundboard, or belly; the bridge thus sustained the direct pull of the strings. In the belly was a circular sound hole, often ornamented with a carved wooden rose. The 16th-century guitar was tuned C–F–A–D′, the tuning of the centre four courses of the lute and of the vihuela.

From the 16th to the 19th century several changes occurred in the instrument. The fifth course of strings was added before 1600; by the late 18th century a sixth course was added. Before 1800, the double courses were replaced by single strings tuned E–A–D–G–B–E′, still the standard tuning.

The guitar is widely played in the folk and popular music of many countries.

In jazz ensembles, it is part of the rhythm section and is occasionally played as a solo instrument. In popular music, the guitar is usually amplified, frequently including more than one instrument, a “lead” guitar, one for rhythm, and a “bass” guitar.