Psychotherapy is the use of psychological methods, particularly when based on regular personal interaction, to help a person change behavior and overcome problems in desired ways. Psychotherapy aims to improve an individual's well-being and mental health, to resolve or mitigate troublesome behaviors, beliefs, compulsions, thoughts, or emotions, and to improve relationships and social skills.

Certain psychotherapies are considered evidence-based for treating some diagnosed mental disorders. Others have been criticized as pseudoscience. There are over a thousand different psychotherapy techniques, some being minor variations, while others are based on very different conceptions of psychology, ethics (how to live), or techniques. Most involve one-to-one sessions, between client and therapist, but some are conducted with groups, including families.