[Page 660]This entry defines two concepts of gender fluidity: (1) a process of changing gender identification over time and (2) an identity label. This entry first describes these two conceptualizations and then discusses how they relate to and diverge from theories of gender development. The entry then discusses the relationship between gender fluidity and sexual orientation to elucidate the complexity and intersectionality of these two constructs. It then provides perspective on the navigation of interpersonal relationships and broader gendered assumptions of Western societies by gender fluid individuals. The entry concludes by considering the potential that the construct of gender fluidity has for enhancing a psychological understanding of gender, providing general directions for how gender fluidity may evolve.