The Unknown Purple is a lost[3] 1923 American silent mystery film that was written and directed by Roland West.

[4][5] After his release from prison, an inventor develops an eerie purple light that renders him invisible, enabling him to seek revenge on his unfaithful wife and his crooked business partner.

The film was adapted from a stage play which was written by Roland West and Carlyle Moore.

[2] In a contemporary review, Variety described the film as an "exceptionally well-made picture - among the best of its type - a mystery.

"[1] The review praised the photography of Oliver Marsh and the acting by Henry Walthall and Alice Lake.