In common law, spousal privilege (also called marital privilege or husband-wife privilege) is a term used in the law of evidence to describe two separate privileges that apply to spouses: the spousal communications privilege and the spousal testimonial privilege.

Both types of privilege are based on the policy of encouraging spousal harmony and preventing spouses from condemning, or being condemned by, their spouses: the spousal communications privilege or confidences privilege is a form of privileged communication that protects the contents of confidential communications between spouses during their marriage from testimonial disclosure, while spousal testimonial privilege (also called spousal incompetency and spousal immunity) protects the individual holding the privilege from being called to testify in proceedings relating to their spouse. However, in some countries, the spousal privileges have their roots in the legal fiction that a husband and wife were one person.

In the United States, federal case law dictates the privileges permissible and prohibited in federal trials, while state case law governs their scope in state courts. A common rule for both the communications privilege and the testimonial privilege is that, "absent a lawful marriage, civil union, or domestic partnership, there is no privilege." Both rules may be suspended depending on the jurisdiction in the case of divorce proceedings or child custody disputes, but are suspended in cases where one spouse is accused of a crime against the other spouse or the spouse's child. Courts generally do not permit an adverse spouse to invoke either privilege during a trial initiated by the other spouse, or in the case of domestic abuse. The privileges may also be suspended where both spouses are joint participants in a crime, depending on the law of the jurisdiction.

In all federal and state courts, a spousal communications privilege applies in both civil and criminal cases. It is far less controversial than the testimonial privilege as it does not originate from the legal fiction that a husband and wife were one person. Instead, it is rooted in the idea that those who are married should feel safe openly communicating with each other without fear of future litigation or criminal proceedings.

In most jurisdictions including in federal courts, both the witness-spouse and the accused-spouse have the spousal communications privilege, so either may invoke it to prevent the witness-spouse from testifying about a confidential communication made during the marriage even if neither spouse is a party in the trial. It covers all communications made during marriage, and cannot be invoked to protect confidential communications between currently married spouses which occurred prior to their marriage. Unlike testimonial privilege, the communications privilege survives the end of a marriage, and may be asserted by a spouse to protect confidential communications that were made during the marriage—even after divorce or death.

The spousal communications privilege may not be invoked if the spouses are suing each other or each other's estates in a civil case; nor if one of the spouses has initiated a criminal proceeding against the other; nor in a competency proceeding regarding one of the spouses. These three scenarios are identical to the limitations which also apply to limit the spousal testimonial privilege. Two further scenarios defeat the spousal communications privilege: if the confidential communication was made in order to plan or commit a crime or fraud, or if a defendant-spouse wishes, in a criminal trial, to testify in their own defense, about a confidential marital communication. In these five situations, a court will not allow either spouse to assert the privilege to block the testimony.^{[citation needed]}

The privilege may not be invoked if the statements were not intended to be confidential. Statements are not confidential if they were made in front of a third party or with the expectation that they would be shared with others. However, the presence of a young child does not negate the confidentiality of the communication. The opposing party must rebut the presumption that confidentiality was intended.

Under U.S. federal common law, the spousal testimonial privilege is held by the witness-spouse, not the party-spouse, and therefore does not prevent a spouse who wishes to testify from doing so. The rationale of this rule is that if a witness-spouse desires to testify against the party-spouse, there is no marital harmony left to protect through the obstruction of such testimony. This common law principle is the view in a minority of U.S. states. A majority of U.S. jurisdictions, however, do not follow U.S. federal common law; in most states, the party-spouse, and not the witness-spouse, is the holder of spousal testimonial privilege.