Joseph Jules Dejerine (August 3, 1849 – February 26, 1917), was a French neurologist.
Joseph Jules Dejerine was born to French parents in Geneva, Switzerland, where his father was a carriage proprietor. During the Franco-Prussian War (1870) Dejerine worked as a volunteer in a Geneva Hospital and in the spring of 1871 decided to pursue his medicine studies in Paris. Following qualification he rose the academic ranks and gained several awards. In 1877 he was appointed to the Hôpital Bicêtre, where he organized a pathological laboratory. He became professeur agrégé in 1886, and he found the opportunity to concentrate his efforts on neurology. He worked at the Hôpital Salpêtrière from 1895, became professor of the history of medicine in 1901 and received a senior appointement at the Salpêtrière in 1911 as professor of neurology at the University of Paris, School of Medicine.
Dejerine was one of the pioneers in the study of localisation of function in the brain, having first shown that word blindness may occur as the result of lesions of the supramarginal and angular gyri.
In 1888 Dejerine married his student, Augusta Marie Klumpke, who had studied medicine in Paris and in 1887 had been the first woman to become interne des hôpitaux. Dejerine died in 1917 at the age of 68 years, physically debilitated by the stress of work in a military hospital during the World War I. The centenary of his birth was commemorated in 1949 at the fourth International Neurological Congress in Paris, when Dejerine's pupil, André Thomas, gave a discourse on his mentor's life and achievements.
Dejerine's numerous publications span a period of more than 40 years. Like many eminent neurologists of his era, Dejerine became interested in psychology in the later stages of his career and he is remembered as a proponent of the view that the personality of the psychotherapist is crucial in any interaction with the patient.