Ewald Hecker (20 October 1843, Halle – 1909) was a German psychiatrist who was an important figure in the early days of modern psychiatry. He is known for research done with his mentor, psychiatrist Karl Ludwig Kahlbaum (1828-1899). The pioneering research of Kahlbaum and Hecker proposed the existence of more than one discrete psychiatric disorder, which contrasted with the concept of "unitary psychosis" that maintained all psychiatric symptoms were manifestations of a single mental disorder.