The Piano Sonata No. 14, by Ludwig van Beethoven, is popularly known as the "Moonlight" Sonata. The work was completed in 1801 and rumored to be dedicated to his pupil, 17-year-old Countess Giulietta Guicciardi, with whom Beethoven was, or had been, in love.

The name "Moonlight" Sonata derives from a description of the first movement by music critic Ludwig Rellstab, who compared it to moonlight shining upon Lake Lucerne.

Source Wikipedia

This first movement is one of the most popular and acclaimed musical pieces over the ages and has seen many interpretations including on the guitar.

The guitar adaptation looses some of the notes in the bass and changes the tonality to A minor since playing this piece in C# Minor, its original tonality, on the guitar would just simply be ungodly and impossible because the instrument doesn't have enough high notes to cover this tonality.