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 Pennsylvania, class action lawsuits are governed by both state and federal law, depending on the jurisdiction of the case. Under Pennsylvania state law, class actions are permitted in accordance with Pennsylvania Rules of Civil Procedure, Rule 1702, which outlines the requirements for maintaining a class action. These requirements include numerosity, commonality, typicality, and adequacy of representation. The purpose of a class action in Pennsylvania is to provide an efficient legal remedy when many individuals have been harmed in a similar way by the same defendant or defendants. On the federal level, class actions that meet certain criteria may be brought under Rule 23 of the Federal Rules of Civil Procedure. Additionally, the Class Action Fairness Act (CAFA) of 2005 allows for certain large class action cases, typically those with claims exceeding $5 million and with plaintiffs and defendants from different states, to be heard in federal court. This is to ensure a more efficient resolution of widespread legal issues and to prevent inconsistent judgments that could arise from separate lawsuits.