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 Montana, as in other states, a mass tort is a type of civil lawsuit where numerous plaintiffs bring similar claims against one or a few defendants. These cases often arise from exposure to harmful substances, defective products, or privacy violations such as data breaches. While mass torts can be filed individually, they are frequently handled as class action lawsuits, which allows for the consolidation of many individual claims into a single action for efficiency and consistency. Montana follows the Federal Rules of Civil Procedure for class actions, which require that the case must meet certain criteria such as having common questions of law or fact, and that the class representatives will adequately protect the interests of the class. Once a case is certified as a class action, it proceeds through the legal system as a single case. It's important to note that mass torts are complex and require the expertise of an attorney with experience in this specialized field of law.