The Piano Sonata No. 14 in C-sharp minor “Quasi una fantasia”, Op. 27, No. 2, popularly known as the Moonlight Sonata, is a piano sonata by Ludwig van Beethoven. It was completed in 1801 and dedicated in 1802 to his pupil, Countess Giulietta Guicciardi.
C小调《准幻想曲》第14钢琴奏鸣曲，作品27，第2号，俗称月光奏鸣曲，是路德维希·范·贝多芬的钢琴奏鸣曲。它于1801年完工，并于1802年献给他的学生朱利埃塔·吉恰尔迪伯爵夫人。