My Sister and I is an apocryphal work attributed to German philosopher Friedrich Nietzsche. Following Nietzsche scholar Walter Kaufmann, most consider the work to be a literary forgery,
It was supposedly written in 1889 or early 1890 during Nietzsche's stay in a mental asylum in the Thuringian city of Jena. If legitimate, My Sister and I would be Nietzsche's second autobiographical and final overall work, chronologically following his Wahnbriefe (Madness Letters), written during his extended time of mental collapse. My Sister and I makes several bold and otherwise unreported biographical claims, most notably of an incestuous relationship between Nietzsche and his sister Elisabeth Förster-Nietzsche, as well as an affair with Richard Wagner's wife Cosima. It is written in a style that combines anecdote and aphorism in a manner similar to other Nietzsche works.