Der Freischütz, Op. 77, J. 277, (usually translated as The Marksman or The Freeshooter) is a German opera with spoken dialogue in three acts by Carl Maria von Weber with a libretto by Friedrich Kind. It premiered on 18 June 1821 at the Schauspielhaus Berlin. It is considered the first important German Romantic opera, especially in its national identity and stark emotionality. The plot is based on the German folk legend of the Freischütz and many of its tunes were inspired by German folk music. Its unearthly portrayal of the supernatural in the famous Wolf's Glen scene has been described as "the most expressive rendering of the gruesome that is to be found in a musical score".

The reception of Der Freischütz surpassed Weber's own hopes and it quickly became an international success, with productions in Vienna the same year followed by Leipzig, Karlsruhe, Prague, other German centres, and Copenhagen. 1824 saw productions in four London theatres in four different adaptations, as well as the French premiere at the Théâtre de l'Odéon as Robin des Bois. Among the many artists influenced by Der Freischütz was a young Richard Wagner. A version in French with recitatives was prepared by Hector Berlioz for a production at the Paris Opera in 1841. This was revived at the Paris Opéra-Comique in 2011.

The overture and the "Huntsmen's Chorus" from act 3 ("With princely enjoyment and manly employment") are often performed as concert pieces.