Emil Wilhelm Georg Magnus Kraepelin (/ˈkrɛpəlɪn/; German: [ˈeːmiːl 'kʁɛːpəliːn]; 15 February 1856 – 7 October 1926) was a German psychiatrist. Fellow psychiatrist Hans Eysenck's Encyclopedia of Psychology identified him as helping to lay the foundation for modern scientific psychiatry, psychopharmacology, and psychiatric genetics.

Kraepelin believed the chief origin of psychiatric disease to be biological and genetic malfunction. His theories dominated psychiatry at the start of the 20th century and, despite the later psychodynamic influence of Sigmund Freud and his disciples, enjoyed a revival at century's end. While he proclaimed his own high clinical standards of gathering information "by means of expert analysis of individual cases", he also drew on reported observations of officials not trained in psychiatry.

His textbooks do not contain detailed case histories of individuals but mosaic-like compilations of typical statements and behaviors from patients with a specific diagnosis. He has been described as a "scientific manager" and "political operator" who developed "a large-scale, clinically oriented, epidemiological research programme". He developed racist psychiatric theories.

Kraepelin, whose father, Karl Wilhelm, was a former opera singer, music teacher, and later successful story teller, was born in 1856 in Neustrelitz, in the Duchy of Mecklenburg-Strelitz in Germany. He was first introduced to biology by his brother Karl, 10 years older and, later, the director of the Naturhistorisches Museum Hamburg.

Kraepelin began his medical studies in 1874 at the University of Leipzig and completed them at the University of Würzburg (1877–1878). At Leipzig, he studied neuropathology under Paul Flechsig and experimental psychology with Wilhelm Wundt. Kraepelin would be a disciple of Wundt and had a lifelong interest in experimental psychology based on his theories. While there, Kraepelin wrote a prize-winning essay, "The Influence of Acute Illness in the Causation of Mental Disorders".

In Würzburg, he completed his Rigorosum (roughly equivalent to a PhD level viva-voce examination, literally "rigorous exam") in March 1878, his Staatsexamen (licensing examination) in July 1878, and his Approbation (his license to practice medicine; roughly equivalent to an MBBS) on 9 August 1878. From August 1878 to 1882, he worked with Bernhard von Gudden at the Ludwig-Maximilians-Universität München.

Returning to the University of Leipzig in February 1882, he worked in Wilhelm Heinrich Erb's neurology clinic and in Wundt's psychopharmacology laboratory. He completed his habilitation thesis - major postdoc publication and process - at Leipzig; it was entitled "The Place of Psychology in Psychiatry". On 3 December 1883, he completed his umhabilitation (habilitation recognition procedure to obtain a "habilitation" at another institution than originally applied for) at the Ludwig-Maximilians-Universität München.

Kraepelin's major work, Compendium der Psychiatrie: Zum Gebrauche für Studirende und Aerzte (Compendium of Psychiatry: For the Use of Students and Physicians), was first published in 1883 and was expanded in subsequent multivolume editions to Ein Lehrbuch der Psychiatrie (A Textbook: Foundations of Psychiatry and Neuroscience). In it, he argued that psychiatry was a branch of medical science and should be investigated by observation and experimentation like the other natural sciences. He called for research into the physical causes of mental illness, and started to establish the foundations of the modern classification system for mental disorders. Kraepelin proposed that by studying case histories and identifying specific disorders, the progression of mental illness could be predicted, after taking into account individual differences in personality and patient age at the onset of disease.