Medical physics is a field of study and practice that applies the facts and principles of physics and engineering to medical practice. It is distinct from biomedical engineering, biophysics and health physics in its focus on patient care. Medical physics is a profession because its practitioners work independently, albeit often as members of a health care team, and we take personal responsibility for the quality of our work.

There are two main specialties within medical physics, therapy and imaging. Therapy is the delivery of ionizing radiation with palliative or curative intent and imaging uses ionizing and nonionizing radiation for diagnostic purposes. Many medical physicists practice all aspects of medical physics, but specialization as a therapeutic radiological physicist, diagnostic radiological physicist, medical nuclear physicist or medical health physicist is becoming more common.