The Mysterious Mister X (German: Der geheimnisvolle Mister X) is a 1936 German comedy film directed by J.A. Hübler-Kahla and starring Ralph Arthur Roberts, Annemarie Steinsieck and Herti Kirchner.^[1]

The film's sets were designed by the art director Gustav A. Knauer and Alexander Mügge.

A British lord, fascinated by crime, spends his time collecting artefacts. He is thrilled when he receives mysterious letters warning that a thief plans to steal a valuable statue from his country house. His secretary persuades him to bring in her fiancée, a private detective, to investigate the case.

• Ralph Arthur Roberts as Lord Wilford
• Mady Rahl as Nelly Taylor, Sekretärin
• Annemarie Steinsieck as Lady Wilford
• Herti Kirchner as Lilian, ihre Tochter
• Curt Ackermann as James - ihr Neffe
• Hermann Thimig as Richard Murray
• Eugen Rex as Smith, Kunsthändler
• Robert Jungk as Duncan - Hausmeister auf Schloß Wilford
• Erwin Biegel as Williams - Diener auf Schloß Wilford
• Willi Schur as Der Nachtwächter auf Schloß Wilford

• Monsieur Breloque a disparu [fr] (1938)
• Trappola d'amore [it] (1940)

• Waldman, Harry. Nazi Films in America, 1933–1942. McFarland, 2008.

• The Mysterious Mister X at IMDb