The Sinister Monk (German: Der unheimliche Mönch) is a 1965 West German thriller film directed by Harald Reinl and starring Karin Dor, Harald Leipnitz and Siegfried Lowitz.

It is based on the 1927 play The Terror by Edgar Wallace and was part of a very successful series of German films inspired by his works.

[1] It was shot at the Spandau Studios in Berlin with location shooting in London, Hamburg and Hamelin in Lower Saxony.

The film's sets were designed by the art directors Walter Kutz and Wilhelm Vorwerg.

[2] The FSK gave the film a rating of 16 and up and found it not appropriate for screenings on public holidays.