Cardenio is a lost play that is believed to have been written by William Shakespeare and John Fletcher in the early 17th century. It is thought to be based on a story from Miguel de Cervantes's novel, Don Quixote, specifically the tale of a character named Cardenio. The play explores themes of love, betrayal, and madness. Although the original text of Cardenio has not survived, references to it exist in historical documents. Scholars have attempted to reconstruct the play based on these references, but no complete version is available. Its significance lies in its connection to both Shakespeare and Cervantes.