A riot is a violent disturbance by a crowd of people. When a riot breaks out, groups of people gather in public places and may destroy property, set fires, attack others, or clash with police. Riots represent a breakdown of normal order, where anger or frustration erupts into chaotic, destructive behavior.

Riots have many causes. Throughout history, some riots have erupted from legitimate grievances about injustice, though the violence itself creates new problems rather than solving old ones. Other riots start after sporting events, when celebrating or disappointed fans get out of control. Some riots begin with protests that spiral into violence, while others erupt spontaneously when social tensions boil over.

A riot goes far beyond mere argument. It involves groups of people acting together in ways they might never act alone, swept up in crowd emotion and mob mentality.

Riot can also mean something wildly successful or entertaining: when a comedian's performance is called a riot, it means the audience found it hilarious. A riot of color describes an explosion of bright, mixed colors, like a garden full of different blooming flowers.