The Kreutzer Sonata is a philosophical novella by Leo Tolstoy that explores the themes of marriage, jealousy, and the nature of love. The story is narrated by a man named Pozdnyshev, who tells a fellow passenger on a train about his unhappy marriage. Pozdnyshev was driven to madness by his jealousy of his wife's supposed infidelity, and he eventually murdered her. The novella is a powerful indictment of the institution of marriage and a meditation on the destructive nature of jealousy.