Diary of a Lost Girl (German: Tagebuch einer Verlorenen) is a 1929 silent film directed by Georg Wilhelm Pabst and starring the American silent star Louise Brooks. It is shot in black and white, and various versions of the film range from 79 minutes to 116 minutes in length. This was Brooks' second and last film with Pabst, and like their prior collaboration (1928's Pandora's Box), it is considered a classic film. The film was based on the controversial and bestselling novel of the same name, Tagebuch einer Verlorenen (1905) by Margarete Böhme. A previous version of the novel, directed in 1918 by Richard Oswald, is now considered a lost film.
Thymian Henning (Louise Brooks), the innocent, naive daughter of pharmacist Robert Henning (Josef Rovenský), is puzzled when their housekeeper, Elizabeth (Sybille Schmitz), leaves suddenly on the day of Thymian's confirmation. It turns out that her father got Elizabeth pregnant. Elizabeth's body is brought to the pharmacy later that day, an apparent suicide, upsetting Thymian.
Thymian's father's assistant Meinert (Fritz Rasp), promises to explain it all to her late that night, but instead seduces her; she gives birth to an illegitimate child.