Carl Maria Friedrich Ernst von Weber (c. 18 November 1786 – 5 June 1826) was a German composer, conductor, virtuoso pianist, guitarist, and critic of the early Romantic period. Best known for his operas, he was a crucial figure in the development of German Romantische Oper (German Romantic opera).

Throughout his youth, his father, Franz Anton, relentlessly moved the family between Hamburg, Salzburg, Freiberg, Augsburg and Vienna. Consequently he studied with many teachers—his father, Johann Peter Heuschkel, Michael Haydn, Giovanni Valesi, Johann Nepomuk Kalcher, and Georg Joseph Vogler—under whose supervision he composed four operas, none of which survive complete. He had a modest output of non-operatic music, which includes two symphonies, two concertos and a concertino for clarinet and orchestra, a bassoon concerto, a horn concertino, two concertos and a Konzertstück for piano and orchestra, piano pieces such as Invitation to the Dance; and many pieces that featured the clarinet, usually written for the virtuoso clarinetist Heinrich Baermann.

His mature operas—Silvana (1810), Abu Hassan (1811), Der Freischütz (1821), Die drei Pintos (comp. 1820–21), Euryanthe (1823), Oberon (1826)—had a major impact on subsequent German composers including Marschner, Meyerbeer, and Wagner; his compositions for piano influenced those of Mendelssohn, Chopin and Liszt. His best known work, Der Freischütz, remains among the most significant German operas.