Client confidentiality is the principle that an institution or individual should not reveal information about their clients to a third party without the consent of the client or a clear legal reason. This concept is commonly provided for in law in most countries.

The access to a client's data as provided by the institution in question is usualy limited to law enforcement agencies and requires some legal procedures to be accomplished prior to such action (eg.: court order issued, etc.). This applies to bank account information or medical record. In some cases the data is by definition inaccessible to third parties and should never revealed, this includes confidential information gathered by attorneys or priests).