This chapter takes the reader on a historical journey from the Ancient Greeks to the present day, explaining how people’s understanding of health and illness changed according to the social context of the time. It describes the traditional model, medical model and social model of health and illness with reference to key players such as Galen, Nightingale, Koch, Lind, Snow, Keys, McKeown, Illich, Black, Marmot and the World Health Organization. The chapter examines the shift from holism to disease to health: the rise of disease prevention and attention to the social determinants of health. It outlines current social-ecological models of health, the life course approach and lay perceptions of health and illness. The chapter describes examples from the twenty-first century: low-grade inflammation, epigenetics, adverse childhood experiences and mindfulness. It concludes by explaining why understanding models of health and illness is central to contemporary health promotion and public health.