Krútňava is an opera in six scenes by Eugen Suchoň written in the 1940s to a libretto by the composer and Štefan Hoza, based on a novella, Za vyšným mlynom (Beyond the Upper Mill) by Milo Urban. The opera was premiered at the Slovak National Theatre, Bratislava, on 10 December 1949.

Suchoň was invited in 1940 to write an opera for the Slovak National Theatre. In 1941 he read Urban's novella Beyond the Upper Mill, a story of love and murder set in the Slovak countryside in the years after World War I, which immediately inspired him. Urban himself however refused to collaborate on the libretto, writing in 1958 that the dramatization risked losing some of the ambiguities he had deliberately created in the book (e.g. the paternity of the heroine's baby).

Suchoň's original conception was to write the opera using two different styles - a quasi-impressionist style to accompany the thoughts of the characters, and a more realistic, nationalist style to accompany external events. Traces of this dualism remain in the score, although Suchoň realised his original ideas were impractical.

Although the premiere was successful, the governing Slovak Communist Party insisted that the original ending be changed to make it more 'optimistic'. Other serious changes were forced on the composer, involving dismantling the very important 'framework' to the opera which posited the story as the result of a wager between the Poet and his Double (spoken roles), and, inevitably, the toning down of any references to Christianity. At first Suchoň refused to make any alterations; the opera was withdrawn from the repertoire. Pressure from his musical colleagues, who realised the importance of the work, induced him to change his mind, and this 'revised version' was performed in Czechoslovakia and abroad in the 1950s, the original ending only being restored in 1963. Complete reconstruction of the original, including the participation of the Poet and his Double, had to await the composer's centenary in 2008, when Suchoň's work as originally conceived was performed in Banska Bystrica.