Human subject research is systematic, scientific investigation that can be either interventional (a "trial") or observational (no "test article") and involves human beings as research subjects, commonly known as test subjects. Human subject research can be either medical (clinical) research or non-medical (e.g., social science) research. Systematic investigation incorporates both the collection and analysis of data in order to answer a specific question. Medical human subject research often involves analysis of biological specimens, epidemiological and behavioral studies and medical chart review studies. (A specific, and especially heavily regulated, type of medical human subject research is the "clinical trial", in which drugs, vaccines and medical devices are evaluated.) On the other hand, human subject research in the social sciences often involves surveys which consist of questions to a particular group of people. Survey methodology includes questionnaires, interviews, and focus groups. All research involving human subjects should be conducted in accordance with three basic ethical principles, namely respect for persons, beneficence and justice.

Human subject research is used in various fields, including research into advanced biology, clinical medicine, nursing, psychology, sociology, political science, and anthropology. As research has become formalized, the academic community has developed formal definitions of "human subject research", largely in response to abuses of human subjects.