In a political era marked by mass public gatherings - from school encampments to streets thick with crowds - why have some counted as protests, while others have been dismissed as senseless riots? Unruly Acts argues that common ideas of protest underestimate the crucial role that public audiences play in making sense of street gatherings and, as a result, misconceive the politics of protest. Drawing on original archival research about two controversial gatherings challenging police brutality and anti-immigrant nativism, Stacey Liou elucidates the agonistic dynamics by which a protest's meanings are created - in protesters' words and deeds, and by disagreements between protesters and audiences as well as audiences themselves. These public acts, interpretations, and disagreements, the book shows, are conditioned by material, collective, and affective criteria of protest. Unruly Acts is a timely examination of the politics of interpretation and the contested social relations that lie at the heart of protest.