Group psychotherapy or group therapy is a form of psychotherapy in which one or more therapists treat a small group of clients together as a group. The term can legitimately refer to any form of psychotherapy when delivered in a group format, including art therapy, cognitive behavioral therapy or interpersonal therapy, but it is usually applied to psychodynamic group therapy where the group context and group process is explicitly utilized as a mechanism of change by developing, exploring and examining interpersonal relationships within the group.

The broader concept of group therapy can be taken to include any helping process that takes place in a group, including support groups, skills training groups (such as anger management, mindfulness, relaxation training or social skills training), and psychoeducation groups. The differences between psychodynamic groups, activity groups, support groups, problem-solving and psychoeducational groups have been discussed by psychiatrist Charles Montgomery. Other, more specialized forms of group therapy would include non-verbal expressive therapies such as art therapy, dance therapy, or music therapy.