A class action is a type of lawsuit in which one or a few plaintiffs seek to represent hundreds or thousands of plaintiffs with the same or similar claims against the same defendants. Rules of procedure in state and federal courts permit class actions in limited circumstances for the purpose of resolving similar disputes more efficiently than if each plaintiff filed a separate lawsuit.

In California, class action lawsuits are governed by the California Code of Civil Procedure (CCP), particularly sections 382 and 1781, as well as by federal law when the case is heard in federal court. These laws allow one or a few plaintiffs, known as class representatives, to sue on behalf of a larger group of individuals who have similar legal claims against the same defendant(s). The purpose of a class action is to provide an efficient and economical way to resolve claims that might be too small for individuals to pursue on their own. To proceed as a class action in California, the case must meet certain criteria, such as demonstrating that the class is so numerous that individual lawsuits would be impractical, there are questions of law or fact common to the class, the claims or defenses of the representative parties are typical of the claims or defenses of the class, and the representative parties will fairly and adequately protect the interests of the class. If a case meets these requirements and is certified as a class action by the court, it allows for the resolution of many similar claims in a single proceeding, potentially benefiting both the plaintiffs and the judicial system by reducing the number of individual cases.