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 New York, mass tort litigation is a legal process that allows numerous plaintiffs who have been similarly harmed by a defendant's actions to join together in a single lawsuit. These cases often involve harm caused by toxic substances, defective products, or privacy violations such as data breaches. While mass torts are similar to class action lawsuits, they differ in that each plaintiff in a mass tort may have individual claims and damages that are distinct from the group, whereas class actions typically involve plaintiffs with nearly identical claims and damages. New York courts handle mass tort cases through a coordinated process to manage the complex legal and logistical issues that arise with such large numbers of plaintiffs. This includes the consolidation of cases for pre-trial proceedings to streamline discovery and other pre-trial activities. The New York State Unified Court System has established procedures and specialized courts, such as the New York City Asbestos Litigation (NYCAL) court, to deal with the unique challenges of mass tort cases. State statutes and federal laws, including rules of civil procedure, govern the filing and conduct of mass tort litigation in New York.