Carl L. Hart (born October 30, 1966) is an American psychologist, neuroscientist, and heroin advocate and user working as the Mamie Phipps Clark Professor of Psychology (in Psychiatry) at Columbia University. Hart is known for his research on drug abuse and drug addiction, his advocacy for the decriminalization of recreational drugs, and his recreational use of drugs. Hart is one of the first tenured African American professors of sciences at Columbia University.