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 South Dakota, as in other states, a mass tort is a type of civil action that involves numerous plaintiffs against one or several defendants. These plaintiffs usually have similar legal claims resulting from the defendant's conduct, such as exposure to hazardous substances, defective products, or privacy violations. Mass torts in South Dakota can be filed as class action lawsuits if they meet certain criteria, such as a large number of plaintiffs, common questions of law or fact, typical claims or defenses of the class, and a representative party that will fairly and adequately protect the interests of the class. These criteria are outlined in the South Dakota Rules of Civil Procedure. If a case is certified as a class action, it allows for a more efficient resolution by consolidating individual claims into a single action. Mass torts are complex and often involve state and federal laws, including statutes that govern product liability, consumer protection, and personal injury.