Judith (Russian: Юдифь, romanized: Yudíf – stress on second syllable) is an opera in five acts, composed by Alexander Serov during 1861–1863.

Derived from renditions of the story of Judith from the Old Testament Apocrypha, the Russian libretto, though credited to the composer, has a complicated history.

The world premiere was given on 16 May 1863 at the Mariinsky Theatre, St. Petersburg, conducted by Konstantin Lyadov and starring Mikhail Sariotti as Holofernes and Valentina Bianki as Judith.

At midday in a square in Bethulia, which is still under siege by Holofernes and his Assyrian troops, the people suffer from despair and thirst.

When he inquires as to her purpose, she pretends that she will show him a secret way to enter and take Bethulia and Jerusalem as long as he allows her to move freely.

Amidst praise of comely Judith, Asfaneses makes an unfortunate remark about her coldness, and is immediately stabbed to death by Holofernes.

In Bethulia the people, awaiting the dawn of the sixth day, are ready to open the gates to the Assyrians, despite pleadings from the high priest.

Besides its success with the public (enhanced by Fyodor Chaliapin's portrayal of Holofernes beginning in 1898), Serov's Judith influenced later Russian composers, including: The Eastern element in Judith is most obvious in Acts III and IV; its influence (presaged by Glinka in Ruslan and Lyudmila) can be detected by comparing the Indian Song from Act IV with the "Song of the Indian Guest" from Rimsky-Korsakov's Sadko.