‘Intellectual disability’ is a widely used psychiatric category that conceives of certain minds as impaired in their development. By approaching intellectual disability from a cross-cultural perspective, anthropology demonstrates how the condition is culturally variable. It shows, in particular, how intellectual disability is produced by different social expectations of ‘normal’ mental development and different ways of responding to adults who do not meet those expectations. Anthropology thus offers a way to analyse this seemingly biological deviation from a universal path of mental development as a growing lack of fit between culturally specific expectations for maturation and a person’s own life course through society. Anthropology also provides innovative research methods that enable a closer understanding of the experiences, lives, and self-narrations of people categorised as having intellectual disabilities themselves—in particular, demonstrating how they develop and exercise agency in spite of considerable constraints. In this way, anthropology gives us a deeper insight into how people become and remain classified as having an intellectual disability, what it is like to live under such categorisations, as well as what such classifications leave out about them as people.