A piece of writing about oneself is a/an

A piece of writing about oneself is an autobiography. Autobiography is a type of literary work that presents a person's life story, typically written in the first-person point of view. It covers important events, experiences, and achievements of the author's life. An autobiography can provide insight into the author's personality, character, and perspective on life. It is different from a biography, which is a written account of someone's life that is written by someone else.