Originating in a 1938 play, the term gaslighting has become part of our everyday vocabulary. But do we truly know what it means? This collection of new and foundational essays explores concepts and experiences of gaslighting from philosophical perspectives. Contributors build on longstanding feminist analyses of the relations among knowledge, affect, and power to consider how gaslighting can work at not only individual but also structural levels to undermine its targets. In examining racial, epistemological, medical, affective, political, and other forms of gaslighting, the book helps illuminate contemporary power relations and provides urgently needed tools for further research in and beyond the field of philosophy.