The Diary of a Young Girl, commonly referred to as The Diary of Anne Frank, is a book of the writings from the Dutch-language diary kept by Anne Frank while she was in hiding for two years with her family during the Nazi occupation of the Netherlands. The family was apprehended in 1944, and Anne Frank died of typhus in the Bergen-Belsen concentration camp in 1945. Anne's diaries were retrieved by Miep Gies and Bep Voskuijl. Miep gave them to Anne's father, Otto Frank, the family's only survivor, just after the Second World War was over.

A diary is a written or audiovisual memorabilic record, with discrete entries arranged by date reporting on what has happened over the course of a day or other period. Diaries have traditionally been handwritten but are now also often digital. A personal diary may include a person's experiences, thoughts, and/or feelings, excluding comments on current events outside the writer's direct experience. Someone who keeps a diary is known as a diarist. Diaries undertaken for institutional purposes play a role in many aspects of human civilization, including government records, business ledgers, and military records. In British English, the word may also denote a preprinted journal format.