Latin memoria 'memory, remembrance') is any nonfiction narrative writing based on the writer's personal memories. The assertions made in the work are thus understood to be factual. Whereas memoir has historically been defined as a subcategory of biography or autobiography since the late twentieth century, the genre is differentiated in form, presenting a narrowed focus, often a particular time section in someone's life or career. A biography or autobiography tells the story "of a life", whereas a memoir usually tells the story of a particular career, occasion, or time, comparable to touchstone moments and turning factors within the author's life. The author of a memoir may be referred to as a memoirist or a memorialist. Memoirs have been written since the ancient occasions, as shown by Julius Caesar's Commentarii de Bello Gallico, often known as Commentaries on the Gallic Wars. Within the work, Caesar describes the battles that befell in the course of the 9 years that he spent preventing native armies within the Gallic Wars.

His second memoir, Commentarii de Bello Civili (or Commentaries on the Civil Struggle) is an account of the occasions that occurred between 49 and forty eight BC in the civil war in opposition to Gnaeus Pompeius and the Senate. The noted Libanius, trainer of rhetoric who lived between an estimated 314 and 394 Advert, framed his life memoir as certainly one of his literary orations, which were written to be learn aloud within the privacy of his study. This type of memoir refers to the concept in ancient Greece and Rome, that memoirs were like "memos", or items of unfinished and unpublished writing, which a author might use as a memory aid to make a extra completed doc later on. The Sarashina Nikki is an instance of an early Japanese memoir, written in the Heian period. A style of guide writing, Nikki Bungaku, emerged throughout this time. Themes of court life, introspection, and emotional expressiveness had been steadily explored in Japanese memoirs