Acceptance and commitment therapy (ACT) is an empirically based form of behavioral and cognitive treatment developed by psychologist Steven C. Hayes. ACT was originally developed to assist with the treatment of anxiety-based disorders but has been applied to numerous behavioral health issues since its conception. ACT is part of what has been called the third wave of behavioral and cognitive therapy, with its focus on mindfulness, acceptance, and values-based living. Since the development of ACT, it has been applied to a wide variety of clinical issues, including couples counseling. This entry provides an overview of the main tenets of this theory, discusses how these tenets are applied in treating couples, and describes the role of an ACT couples counselor.