Creutzfeldt–Jakob disease (CJD), also known as subacute spongiform encephalopathy or neurocognitive disorder due to prion disease, is an invariably fatal degenerative brain disorder. Early symptoms include memory problems, behavioral changes, poor coordination, and visual disturbances. Later symptoms include dementia, involuntary movements, blindness, weakness, and coma. About 70% of people die within a year of diagnosis. The name Creutzfeldt–Jakob disease was introduced by Walther Spielmeyer in 1922, after the German neurologists Hans Gerhard Creutzfeldt and Alfons Maria Jakob.

CJD is caused by a type of abnormal protein known as a prion. Infectious prions are misfolded proteins that can cause normally folded proteins to also become misfolded. About 85% of cases of CJD occur for unknown reasons, while about 7.5% of cases are inherited in an autosomal dominant manner. Exposure to brain or spinal tissue from an infected person may also result in spread. There is no evidence that sporadic CJD can spread among people via normal contact or blood transfusions, although this is possible in variant Creutzfeldt–Jakob disease. Diagnosis involves ruling out other potential causes. An electroencephalogram, spinal tap, or magnetic resonance imaging may support the diagnosis.

There is no specific treatment for CJD. Opioids may be used to help with pain, while clonazepam or sodium valproate may help with involuntary movements. CJD affects about one person per million people per year. Onset is typically around 60 years of age. The condition was first described in 1920. It is classified as a type of transmissible spongiform encephalopathy. Inherited CJD accounts for about 10% of prion disease cases. Sporadic CJD is different from bovine spongiform encephalopathy (mad cow disease) and variant Creutzfeldt–Jakob disease (vCJD).