This paper investigates the link between social media and hate crime using hand-collected data from Facebook and Twitter. We study the case of Germany, where the recently emerged right-wing party Alternative für Deutschland (AfD) has developed a major social media presence. Using a difference-in-differences design, we show that right-wing anti-refugee sentiment on Facebook predicts violent crimes against refugees in otherwise similar municipalities with higher social media usage. Consistent with social media being the driving force, the effect decreases with internet outages; increases with user network interactions; is not driven by the news cycle; and does not hold for posts unrelated to refugees. We find similar evidence for the United States, where President Trump’s twitter activity strongly predicts hate crimes against the minorities targeted in his tweets, but not other minorities. We find no effect for the period before Trump’s presidential campaign or measures of general anti-minority sentiment.