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 Washington State, class action lawsuits are governed by both state and federal law, depending on the jurisdiction of the case. Under the Washington Civil Rule (CR) 23, which closely mirrors the Federal Rule of Civil Procedure 23, a class action can be brought if there is a large number of individuals (so many that it is impracticable to bring them all before the court) who have claims or defenses that are typical of the class, and the representatives' claims or defenses are typical of the class. Additionally, the representatives must fairly and adequately protect the interests of the class. Class actions in Washington are used to increase the efficiency of the legal process by allowing a group of individuals with common legal issues to address their grievances in a single lawsuit rather than through multiple individual suits. This can be particularly useful in consumer protection cases, employment disputes, and other areas where individual claims might be too small to justify separate lawsuits. If the case involves federal questions or parties from different states and meets the monetary threshold, it may be brought in or removed to federal court under the Class Action Fairness Act (CAFA).