General paresis, also known as general paralysis of the insane (GPI), paralytic dementia, or syphilitic paresis is a severe neuropsychiatric disorder, classified as an organic mental disorder and is caused by late-stage syphilis and the chronic meningoencephalitis and cerebral atrophy that are associated with this late stage of the disease when left untreated. GPI differs from mere paresis, as mere paresis can result from multiple other causes and usually does not affect cognitive function. Degenerative changes caused by GPI are associated primarily with the frontal and temporal lobar cortex. The disease affects approximately 7% of individuals infected with syphilis, and is far more common in third world countries where fewer options for timely treatment are available. It is more common among men.

GPI was originally considered to be a type of madness due to a dissolute character, when first identified in the early 19th century. The condition's connection with syphilis was discovered in the late 1880s. Progressively, with the discovery of organic arsenicals such as Salvarsan and Neosalvarsan (1910s), the development of pyrotherapy (1920s), and the widespread availability and use of penicillin in the treatment of syphilis (1940s), the condition was rendered avoidable and curable. Prior to this, GPI was inevitably fatal, and it accounted for as much as 25% of the primary diagnoses for residents in public psychiatric hospitals.