Defeat is the loss of justification for believing something in light of new information. This Element mainly aims to work towards developing a novel account of defeat. It distinguishes among three broad views in the epistemology of defeat: scepticism, internalism, and externalism and argues that that sceptical and internalist accounts of defeat are bound to remain unsatisfactory. As a result, any viable account of defeat must be externalist. While there is no shortage of externalist accounts, the Element provides reason to think that extant accounts remain unsatisfactory. The Element also explains the constructive tasks of developing an alternative account of defeat and showing that it improves on the competition.