Social movements are associated with many large societal changes, but evidence of their causal effects is limited. We study the effect of the MeToo movement on an important personal decision—reporting a sex crime to the police. We construct a new quarterly dataset of crimes reported in 31 OECD countries and analyze the effect of the MeToo movement by employing a triple-difference strategy over time, across countries with strong and weak MeToo movements, and between crime types. The movement increased reporting of sex crimes by 10% during its first six months. The effect persists until the end of our data, more than a year after the movement started. Using more detailed US data, we show that the MeToo movement not only increased reporting, but also increased arrests for sexual assaults. In contrast to a common criticism of the movement, we do not find evidence for large differences in the effect across racial and socioeconomic groups. Based on additional survey and crime data, we show that the increased reporting reflects a higher propensity to report sex crimes, and not an increase in the incidence of sex crimes. The mechanism most consistent with our results is that victims were more motivated to report sex crimes because individuals perceived sexual misconduct to be a more serious problem following the MeToo movement. Our results demonstrate that social movements can rapidly and persistently change high-stakes personal decisions.