Some harms scatter across so many people that individual lawsuits are impractical. A class action is a lawsuit in which one or more representative plaintiffs sue on behalf of a larger group of people who share common legal claims.

Courts must certify that the class meets requirements such as numerosity, commonality, typicality, and adequate representation. Notice to class members and, in many cases, the chance to opt out protect individual interests. Settlements and judgments bind the class when approved by the court.

Class actions are common in consumer, securities, employment, and mass-tort contexts. They aggregate small claims into a viable case and promote consistent treatment of similar injuries. Critics raise concerns about attorney fees and the quality of representation; procedural rules attempt to police those risks.

• Lawsuit on behalf of a group with common claims
• Requires court certification of the class
• Can bind members through judgment or settlement
• Used for widespread but individually small harms