Of the many social scientists who have contributed to the field of health and healthcare, few have shaped thought to the extent that the French philosopher and historian Michel Foucault (1926-83) has. Foucault’s work has been influential internationally not only because he wrote specifically about health and medicine, but because his work, which traversed many topics (such as the history of crime and punishment, sexuality, and the formation of knowledge), offered a rich ‘toolkit’ of ideas that may be taken up and applied in understanding diverse issues within the arena of health and healthcare; for example, responses to disability, practices of body modification, the impacts of new biomedical technologies, the practices of dentistry. The ‘Foucault effect’ is evident in many disciplines or fields of study that touch on questions of health, including sociology, anthropology, social policy, business and marketing, medical education and communication studies. This effect can be explained by the fact that Foucault offered critical perspectives on matters of wide concern, both challenging taken-for-granted ways of understanding and offering a new agenda for research and policy. Foucault’s legacy is difficult to neatly summarise since it informs the work of many writers to varying degrees, and not always explicitly. This chapter examines some of the key concepts developed by Foucault and how these have been and may be applied by researchers in the fields of health and healthcare. To begin, it is important to understand the kind of theorist that Foucault was and how his way of thinking differed from, say, Marxists or theorists of modernity. All writers are products of their time, generating work that reflects the preoccupations and values of their society and, although he was a critical thinker, like other writers, Foucault had his biases and ‘blind spots’, which we need to recognise.