This is an open access title available under the terms of a [CC BY-NC-ND 4.0 International] licence. It is free to read at Oxford Clinical Psychology Online and offered as a free PDF download from OUP and selected open access locations.The theory of mentalizing and epistemic trust introduced by Peter Fonagy and colleagues at the Anna Freud Centre has been an important perspective on mental health and illness. Mentalizing and Epistemic Trust is the first comprehensive account and evaluation of this perspective. The book explores twenty primary concepts that organize the contributions of Fonagy and colleagues: adaptation, aggression, the alien self, culture, disorganized attachment, epistemic trust, hypermentalizing, reflective function, the P factor, pretend mode, the primary unconscious, psychic equivalence, mental illness, mentalizing, mentalization-based therapy, non-mentalizing, the self, sexuality, the social environment, and teleological mode. The biographical and social context of the development of these ideas is examined. The book also specifies the current strengths and limitations of the theory of mentalizing and epistemic trust, with attention to the implications for both clinicians and researchers.This book will be of interest to historians of the human sciences, developmental psychologists, and clinicians interested in taking a broader perspective on psychological theory and concepts.