Sigbert Josef Maria Ganser (24 January 1853, Rhaunen, Rhine Province – 4 January 1931, Dresden, Saxony) was a German psychiatrist born in Rhaunen.

Afterwards he worked briefly at a psychiatric clinic in Würzburg, and later as an assistant to neuroanatomist Bernhard von Gudden (1824-1886) in Munich.

In 1886, he became head of the psychiatric department at Dresden General Hospital.

The features included approximate or nonsensical answers to simple questions, perceptual abnormalities, and clouding of consciousness.

Ganser believed that these symptoms were an associative reaction caused by an unconscious attempt by the patient to escape from an intolerable mental situation.