Pizzagate. The Bowling Green Massacre. Pope Francis endorsing Donald Trump for president. How should we combat such “fake news” stories, which often go viral? As cognitive scientists, we view this problem through the lens of what we know about the construction, representation, and updating of belief and knowledge more generally. That is, we argue that the same efficient processes that support the learning of veridical information also support the processing of fake news and sometimes produce false beliefs. Anchoring on the larger psychological literature on belief and knowledge highlights possible solutions while casting doubt on other possible interventions. For example, we are not optimistic about interventions that focus learners on assessing the credibility of information sources, given that such information is likely forgotten over time. Overall, we argue that the basic science of belief and knowledge provides a useful foundation for thinking about reactions to and consequences of fake news.