Kosiki is an opéra comique in three acts, with music by Charles Lecocq and words by William Busnach and Armand Liorat. It was first produced at the Théâtre de la Renaissance, Paris, on 18 October 1876, with a cast headed by Zulma Bouffar and Jean-François Berthelier. By the standards of Lecocq's biggest successes its initial run of 75 performances was a disappointment.
The opera is set in Japan at an unspecified historical period, and depicts the attempt of a member of the imperial family to seize the throne by abducting the true heir and substituting a female baby. The abducted heir is found and all ends well.