Piano Sonata No. 14, commonly known as the "Moonlight Sonata," is a famous piano composition by Ludwig van Beethoven. Completed in 1801, it is part of his early piano sonatas and is notable for its expressive depth and innovative structure. The sonata consists of three movements, with the first movement being particularly well-known for its serene and haunting melody. The first movement, marked "Adagio sostenuto," is often associated with a calm, reflective mood, while the second movement, "Allegretto," provides a contrasting lightness. The final movement, "Presto agitato," is energetic and dramatic, showcasing Beethoven's mastery of the piano. This sonata remains a staple in the classical piano repertoire.