John Charles Turner (September 7, 1947 – July 24, 2011) was a British social psychologist who, along with colleagues, developed the self-categorization theory. Amongst other things the theory states that the self is not a foundational aspect of cognition, but rather that the self is an outcome of cognitive processes and an interaction between the person and the social context. Self categorization theory was developed as a companion theory to the Social identity theory, and the two theories taken together are known as the social identity approach.