Health psychology is concerned with understanding how biology, behavior, and social context influence health and illness. Health psychologists work alongside other medical professionals in clinical settings, work on behaviour change in public health promotion, teach at universities, and conduct research. Although its early beginnings can be traced to the kindred field of clinical psychology, four different divisions within health psychology and one allied field have developed over time: clinical health psychology, occupational health psychology(an allied field),public health psychology, community health psychology, and critical health psychology.

Psychologists who strive to understand how biological, behavioral, and social factors influence health and illness are called health psychologists. The term "health psychology" is often used synonymously with the terms "behavioral medicine" and "medical psychology". Health psychologists work with many different health care professionals (e.g., physicians, dentists, nurses, physician's assistants, dietitians, social workers, pharmacists, physical and occupational therapists, and chaplains) to conduct research and provide clinical assessments and treatment services. Many health psychologists focus on prevention research and interventions designed to promote health and reduce the risk of disease. While more than half of health psychologists provide clinical services as part of their duties, many health psychologists function in non-clinical roles, primarily involving teaching and research.