Widespread bias and discrimination based on weight have been documented in key areas of living, including education, employment, and health care. This paper examines the social and psychological origins of this bias through a review and critique of theoretical and empirical literatures, and proposes how the field might best advance in the area of reducing stigma. Explanations for the development and reduction of weight stigma are examined with different theoretical approaches, including attribution theory and a social consensus model. Individual and sociocultural contributors to bias suggested by these approaches are highlighted. New directions are discussed in both the understanding and prevention of weight bias.