Attorney–client privilege or lawyer–client privilege is the name given to the common law concept of legal professional privilege in the United States. Attorney–client privilege is "[a] client's right to refuse to disclose and to prevent any other person from disclosing confidential communications between the client and the attorney.

n. the requirement that an attorney may not reveal communications, conversations and letters between himself/ herself and his/her client, under the theory that a person should be able to speak freely and honestly with his/her attorney without fear of future revelation. In a trial, deposition, and written questions (interrogatories), the attorney is required and the client is entitled to refuse to answer any question or produce any document which was part of the attorney-client contact. The problem sometimes arises as to whether the conversation was in an attorney-client relationship. If a man tells his neighbor who happens to be an attorney that he embezzled funds, is he doing so while seeking legal advice or just chatting over the fence (which is the test)? If a document was prepared as part of the legal preparation for a client, it usually is a "work product" and is also privileged. Similar privileges exist between pastor and parishioner and doctor and patient. See also: attorney's work product privileged communication work product

In common law jurisdictions, legal professional privilege protects all communications between a professional legal adviser (a solicitor, barrister or attorney) and his or her clients from being disclosed without the permission of the client. The privilege is that of the client and not that of the lawyer.