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.

This piece is one of Beethoven’s most popular compositions for the piano, and it was a popular favorite even in his own day. Beethoven wrote the Moonlight Sonata in his early thirties, after he had finished with some commissioned work.
升c小调第十四钢琴奏鸣曲，俗称月光奏鸣曲，是贝多芬的钢琴奏鸣曲。 它于1801年完成，并于1802年献给他的学生，朱丽叶塔Guicciardi伯爵夫人。

这件作品是贝多芬最受欢迎的钢琴作品之一，即使在他自己的时代也很受欢迎。 贝多芬在完成了一些委托工作之后，在三十出头就写下了月光奏鸣曲。