The Piano Sonata No. 14 in C? minor "Quasi una fantasia", Op. 27, No. 2, by Ludwig van Beethoven, popularly known as the Moonlight Sonata (Mondscheinsonate in German), is one of Beethoven's most popular piano sonatas, as well as one of his most famous compositions for the piano. Completed in 1801, the sonata was dedicated in 1802 to his pupil, the then 20-year-old Countess Julie Guicciardi, with whom Beethoven was, or had briefly been, in love, and who was also first suspected to have been the composer's Immortal Beloved.