(Latin: “friend of the court”), one who assists the court by furnishing information or advice regarding questions of law or fact. He is not a party to a lawsuit and thus differs from an intervenor, who has a direct interest in the outcome of the lawsuit and is therefore permitted to participate as a party to the suit.

An amicus curiae normally may not participate except by leave of the court, and most courts seldom permit persons to appear in such a capacity. The Supreme Court of the United States, however, permits federal, state, and local governments to submit their views in any case that concerns them without obtaining the consent of either the court or the parties. Private persons may appear as amici curiae in the Supreme Court, either if both parties consent or if the court grants permission.