Plaintiff

A plaintiff is a party who initiates a civil lawsuit by filing a complaint with a court, alleging that another party, the defendant, has caused them legal harm and seeks relief such as damages, restitution, or an injunction. The term is used primarily in common law jurisdictions; in some places the plaintiff may be called the claimant or petitioner.

In civil actions, the plaintiff sets out the factual and legal basis for the claim and serves the complaint on the defendant. The plaintiff bears the burden of proof to establish liability by the applicable standard (for example, a preponderance of the evidence in many cases), though some claims or defenses may require higher standards. The complaint also outlines the remedies sought and any statutory or contractual theories supporting the relief requested.

During litigation, the defendant responds with an answer and defenses, may move to dismiss, and may assert counterclaims. The dispute then proceeds through stages such as discovery, motions, and, if unresolved, trial. The plaintiff may seek class certification in appropriate cases or pursue settlements at any stage.

In some jurisdictions, civil plaintiffs may be represented by attorneys or appear pro se. In criminal proceedings, the comparable initiating party is the prosecution or state, not the plaintiff, and the terminology differs accordingly.

Etymology traces the term to Old French plaintif, meaning “complainant,” from a root related to plaint or complaint, reflecting the plaintiff’s role as the one who brings a claim to the court.