We aim to move the externalism and self-knowledge debate forward by exploring two novel sceptical challenges to the prospects of self-knowledge of a paradigmatic sort, both of which result from ways in which our thought content, cognitive processes and cognitive successes depend crucially on our external environments. In particular, it is shown how arguments from extended cognition (e.g., Clark A, Chalmers D. Analysis 58:7–19 (1998); Clark A. Supersizing the mind: Embodiment, action, and cognitive extension. Oxford: Oxford University Press (2008)) and situationism (e.g., Alfano M. The Philosophical Quarterly 62:223–249 (2012), Alfano M. Expanding the situationist challenge to reliabilism about inference. In Fairweather A (ed) Virtue epistemology naturalized, Springer, Dordrecht, pp 103–122 (2014); Doris JM. Noûs 32:504–530 (1998), Doris JM. Lack of character: Personality and moral behavior. Cambridge University Press, Cambridge (2002); Harman G. Proceedings of the Aristotelian Society. 99:315–331 (1999), Harman G. Proceedings of the Aristotelian Society 100:223–226 (2000)) pose hitherto unexplored challenges to the prospects of self-knowledge as it is traditionally conceived. It is shown, however, that, suitably understood, these apparent challenges in fact only demonstrate two ways in which our cognitive lives can be dependent on our environment. As such, rather than undermining our prospects for attaining self-knowledge, they instead illustrate how self-knowledge can be extended and expanded.