A legal and ethical obligation imposed on the recipient of information provided by another person (the provider) not to use that information for any purpose other than that for which the information was provided. The obligation can arise from a relationship or from a contract and applies to all information that is provided and that is not publicly available, whether or not the information identifies the provider. The relationships that are recognised to involve the obligation are typically between professionals and clients or patients.

Although it is not settled whether the relationship between research and research participants, of itself, involves the same obligation, researchers commonly define the degree of confidentiality that will be offered as a term of consent for participation. Researchers need to be aware of the possibilities not only of external confidentiality (as described in this entry) but also of internal confidentiality, that is, the inadvertent disclosure of information among research participants.

The obligation can be superseded by the need to use the information to serve a public interest, such as the protection of children, prevention of the spread of infectious disease, the conduct of court proceedings and the investigation of serious criminal offences. In such circumstances, researchers can be compelled to disclose information that was collected in confidence. (see also Privacy; Public Interest; Transparency)