This paper quantifies how much of violent crime in society can be attributed to football-related violence. Exploiting rich crime register data, we study the universe of professional football matches played out in Germany’s top three football leagues over the period 2011–2015. Our main result shows that violent crime increases by 17 percent on a match day, with associated social costs of roughly 58 million euros annually. Exploring possible mechanisms, we find that the match day effect can be attributed to violence among males in the 18–39 age group, rises to 63 percent on days with high-rivalry derby matches, and that a non-negligible share of it stems from violent crimes committed by group offenders and assaults on police officers. Most of the facts we document can be accommodated by social identity explanations of football hooliganism, while frustration-aggression theories of sports-related violence can explain only some of the findings in isolation.