"L. van Beethoven: Sonata No. 16 in G Major, Op. 31 No. 1" is the title of a work based on the analysis of Beethoven's sixteenth sonata, written at the beginning of the middle period of the composer's creativity, between 1801 and 1802. It is a three-movement sonata that introduces new musical ideas uncommon for the Classical period. The second theme of the first movement (Allegro vivace) is written in B major and B minor, which are the mediants of the original key - G major - something that was unusual for most sonatas of that time. The first movement is written in sonata form, the second in ABA three-part musical form in the subdominant key of C major, and the final movement in rondo form in the original key of G major. The slow second movement represents the most ornamented ABA form in all of L. van Beethoven's works, and besides ornaments, the sonata employs trills, polyphonic imitation techniques, passages, and small note values. The first sonata in opus 31 is light and airy, with hints of humor and irony, making it difficult to explain why, despite this, it is not one of the more well-known and highly regarded sonatas. In addition to the analysis of each movement, this paper presents the life and work of L. van Beethoven, as well as his opus, which is divided into three periods: early, middle, and late creative period. He is considered the founder of Romanticism and one of the greatest figures in the history of music.