A psychiatrist is a physician (M.D. or D.O.) who specializes in the diagnosis, treatment, and prevention of mental illnesses and substance use disorders. Psychiatrists are the only mental health professionals who can prescribe medications and admit to hospitals.

In order to become a psychiatrist, one must graduate from college and then medical school, and go on to complete four years of residency training in the field of psychiatry.

Psychiatrists may undergo additional training to further specialize in such areas as child and adolescent psychiatry, geriatric psychiatry, forensic (legal) psychiatry, administrative psychiatry, addiction psychiatry, emergency psychiatry, psychiatry in general medical settings (consultation/liaison psychiatry), mental retardation/developmental disability, community psychiatry and public health, military psychiatry and psychiatric research. Some choose additional training in psychoanalysis at special psychoanalytic institutes.