A mass tort is a civil lawsuit that involves hundreds or thousands of plaintiffs and one or a few defendants in which the plaintiffs have the same or similar claims against the defendant or defendants. Mass tort lawsuits are often filed as class action lawsuits (a procedural mechanism for joining the plaintiffs in one lawsuit), and are typically based on alleged wrongful acts (torts) such as exposure of the plaintiffs to harmful substances (asbestos or benzene), or defective products (pharmaceuticals or medical devices), or invasions of privacy (data breaches).

In Massachusetts, a mass tort is a type of civil litigation that allows a large number of plaintiffs to sue one or a few defendants for similar claims of harm. These cases often arise from exposure to harmful substances, defective products, or privacy violations such as data breaches. While mass torts can be filed as class action lawsuits, they are distinct in that each plaintiff may have unique damages and the cases are often treated individually. Massachusetts state statutes and federal laws govern the procedures for filing and managing mass tort claims. The Massachusetts Rules of Civil Procedure, along with the Federal Rules of Civil Procedure when in federal court, provide the framework for such lawsuits, including the consolidation of cases and the certification of a class action. Plaintiffs in mass tort cases must demonstrate that the defendant's actions caused their injuries, and they may seek compensatory and punitive damages. It is important for plaintiffs to consult with an attorney experienced in mass torts to navigate the complexities of these cases.