Tagebuch einer Verlorenen (or The Diary of a Lost Girl) is a book by the German author Margarete Böhme (1867–1939).

It purportedly tells the true story of Thymian, a young woman forced by circumstance into a life of prostitution.

[1] One contemporary scholar has called it "Perhaps the most notorious and certainly the commercially most successful autobiographical narrative of the early twentieth century".

The book remained in print more than 25 years, until it was driven out-of-print by groups seeking to suppress it at the beginning of the Nazi era.

In Tagebuch einer Verlorenen, Thymian turns to a life of prostitution after being seduced by her father's assistant and suffering the scorn of her family and neighbors.

A five-act stage play based on Tagebuch einer Verlorenen was authored by Wolf von Metzlch-Schilbach.

In the wake of the success of Tagebuch einer Verlorenen, a number of similarly themed, lower class, women's autobiographies were also published.

[9] And the American novelist Henry Miller included The Diary of a Lost One on his list of the books which influenced him the most.

[11] Some years later, in his 1946 book From Caligari to Hitler: A Psychological History of the German Film, the critic Siegfried Kracauer commented on the Pabst film and its literary source – "the popularity of which among the philistines of the past generation rested upon the slightly pornographic frankness with which it recounted the private life of some prostitutes from a morally elevated point of view".

It is difficult for me to believe that a grown man or woman with a straight mind and a clean heart can find anything that is not of good influence in this most moving, most convincing, most poignant story of a great-hearted girl who kept her soul alive amidst all the mire that surrounded her poor body".

It was first advertised as The Diary of a Lost Soul, the title given it by its translator, the Irish author Ethel Colburn Mayne (1865-1941).

[15] After having been out-of-print in English for more than 100 years, the book was reissued in the United States as The Diary of a Lost Girl in 2010.