Steven C. Hayes (born August 12, 1948) is an American clinical psychologist and Nevada Foundation Professor at the University of Nevada, Reno Department of Psychology, where he is a faculty member in their Ph.D. program in behavior analysis, and coined the term clinical behavior analysis. He is known for devising a behavior analysis of human language and cognition called relational frame theory, and its clinical application to various psychological difficulties, such as anxiety. Hayes also developed a widely used and evidence-based procedure often used in counseling called acceptance and commitment therapy (ACT), which relies heavily on counterconditioning techniques, such as mindfulness (a private behavior in radical behaviorism), and positive reinforcement.