I defend a new account of conspiracy theories, which identifies the epistemological features that make them a socially relevant—and worrisome—phenomenon in our society. On my view, a conspiracy theory is an individual or group belief in a conspiracy which is resistant to disconfirmation by evidence. My approach diverges from the dominant accounts discussed in the literature in two major ways. First, rather than discussing conspiracy theories as a type of theory about a conspiracy, I focus on conspiracy theories as a type of belief in a conspiracy, namely, one that resists revision in light of new evidence. Secondly, conspiracy theories on my view are not only an individual phenomenon, but also, importantly, a collective one. The account I propose, and the shift in focus it produces, provides a new framework for understanding and addressing the phenomenon of conspiracy theories as a problem in our society with deep implications for our political environments.