Here, I first analyze gender identity qua gender self-ascription and offer a theory of the psychological states underpinning gender self-ascriptions, which I call a form of ‘self-identification’. I hold gender self-identification consists of a gender self-concept, which itself consists of a belief or assumption in a context, and sometimes involves a gender role ideal, which consists of an individual’s expectations and standards for how to perform a gender role. Second, I defend my view from an objection to similar views like it, which amounts to the claim that they cannot explain nonbinary gender identities, by showing how my account explains various nonbinary gender identities in psychological terms. Finally, I show how my view can begin stabilizing the construct of gender identity in neuroscience by helping researchers foster agreement on how to define gender identity and what methods are best to study it.