A dissenting opinion (or dissent) is an opinion in a legal case in certain legal systems written by one or more judges expressing disagreement with the majority opinion of the court which gives rise to its judgment.

Dissenting opinions are normally written at the same time as the majority opinion and any concurring opinions, and are also delivered and published at the same time. A dissenting opinion does not create binding precedent nor does it become a part of case law, though they can sometimes be cited as a form of persuasive authority in subsequent cases when arguing that the court's holding should be limited or overturned. In some cases, a previous dissent is used to spur a change in the law, and a later case may result in a majority opinion adopting a particular understanding of the law formerly advocated in dissent. As with concurring opinions, the difference in opinion between dissents and majority opinions can often illuminate the precise holding of the majority opinion.

The dissent may disagree with the majority for any number of reasons: a different interpretation of the existing case law, the application of different principles, or a different interpretation of the facts. Many legal systems do not provide for a dissenting opinion and provide the decision without any information regarding the discussion between judges or its outcome.

A dissent in part is a dissenting opinion which disagrees selectively with one or more parts of the majority holding. In decisions that require holdings with multiple parts due to multiple legal claims or consolidated cases, judges may write an opinion "concurring in part and dissenting in part".