This article proposes that social identities are best understood as a kind of affordance, a “social identity affordance.” Social identity affordances are possibilities for action and interaction between persons, within a social niche, based on perceived and self-perceived social group identification. First, the view presented captures and articulates the basic structure of social identities. Second, it explains the multifaceted interplay of such an item in the social field, including not only the complexity of the interpersonal dimensions, but also the multiplicity (...) of registers in which social identities vibrate (ethical, political, psychological, geographical, affective, epistemic). Third, by doing good on (i) and (ii), the view makes social identities intelligible, helping preclude reductive misinterpretations of social identities, either subjective-only or public-only. The view has robust descriptive and explanatory power in concrete social contexts and retains the openness of a historically bound type of formation whose specific meanings change over time. (shrink)