It is common nowadays for laypeople to take public stances on complex issues, such as the effectiveness of a vaccine or the seriousness of anthropogenic climate change, without any kind of disciplinary expertise. Yet those who do so act as if they were experts in the field, disseminating their thoughts and sometimes also spreading their advice. Scholars have ascribed this phenomenon to various kinds of individuals, such as conspiracy or contrarian thinkers, science denialists, know-it-all experts and celebrities. This paper aims (...) to argue that behind such different manifestations lies a common, independently identifiable epistemic disposition that will be called epistemic hubris that will be fully explained in relation to other epistemic vices already discussed in the literature. Epistemic hubris includes, but is not limited to, overconfidence; it may or not entail arrogance; it is similar to yet distinct from hyper-autonomy and conspiracy thinking. Its peculiarity is that individuals who develop it seem to believe that they can easily become experts, even without special training. This disposition negatively affects individuals’ epistemic conduct, hindering knowledge and true belief formation, and can generate morally relevant consequences when people who falsely consider themselves experts begin to share their mistaken beliefs. (shrink)