The Blue Mountains Mystery is a lost 1921 Australian silent film directed by Raymond Longford and co-directed by Lottie Lyell.

[7] The Blue Mountains Mystery involves the alleged murder of a wealthy businessman, Henry Tracey, and the eventual discovery that the victim was an underworld look-alike impersonator.

"[10] The movie was produced by the Carroll brothers, EJ and Dan, who had previously backed Longford's The Sentimental Bloke.

According to the book Australian Cinema: The First 80 Years by Graham Shirley and Brian Adams, the film cost almost double that of The Sentimental Bloke (1919).

[4][16] In November 1921 Everyones reported the film "is playing to very big business all along the line, the patrons being more than satisfied with a picture that makes more than an Australian appeal.

The story itself is somewhat melodramatic in construction here and there, but there is nothing unduly sensational, and the mystery is sufficiently enveloped in doubt to keep the audience guessing as to whom the original culprit is... the picture must have cost a great amount of money to produce.

[22]Triad called it an "uninteresting and disconnected" picture before stating, "Mr. Longford may be an excellent man when it comes to producing back-block studies and Woolloomooloo types; but he has not the vaguest beginning of an idea how to direct men and women in what is termed manners of society.

[24] The London Bioscope wrote of The Blue Mountains Mystery: " …by its restrained acting, shows the force which a story gains in the telling.

"[27] The November 1921 edition of the Picture Show magazine also praised Lyell as being "enthusiastic, original, possessing charm and common sense" for her writing of the screenplay.

[28] Dan Carroll expressed satisfaction with the film and said he wanted to do another movie with Longford, Lyell and Arthur Tauchert in the vein of The Sentimental Bloke.