The vihuela (Spanish pronunciation: [biˈwela]) is a 15th-century fretted plucked Spanish string instrument, shaped like a guitar (figure-of-eight form offering strength and portability) but tuned like a lute. It was used in 15th- and 16th-century Spain as the equivalent of the lute in Italy and has a large resultant repertory.
There were many different plucked instruments[15] that were being invented and used in Europe, during the Middle Ages. By the 16th century, most of the forms of guitar had fallen off, to never be seen again. However, midway through the 16th century, the five-course guitar[16] was established. It was not a straightforward process.
Finally, c. 1850, the form and structure of the modern guitar were developed by different Spanish makers such as Manuel de Soto y Solares and, perhaps the most important of all guitar makers, Antonio Torres Jurado, who increased the size of the guitar body, altered its proportions, and invented the breakthrough fan-braced pattern. Bracing, the internal pattern of wood reinforcements used to secure the guitar’s top and back and prevent the instrument from collapsing under tension, is an important factor in how the guitar sounds. Torres’ design greatly improved the volume, tone, and projection of the instrument, and it has remained essentially unchanged since.
I’m pretty sure that the guitar is a relatively-recent instrument.
goes looking
It looks like the modern guitar didn’t exist, but apparently there were predecessor instruments around:
https://en.wikipedia.org/wiki/Vihuela
https://en.wikipedia.org/wiki/Guitar