In this invited article, I present an inclusive theory of gender that clarifies its interconnections with gender identity, gender expression, and sexuality. To support this functionalist theory, I summarize findings from an extensive body of mixed methods research on lesbian, gay, bisexual, transgender, queer, and other (LGBTQþ) genders in the United States. I use a feminist-intersectional lens to empirically base and historically situate a theory of gender that is grounded in research of LGBTQþ communities (butch, femme, bear, leathermen, transgender, drag queens, and family/house systems). I define genders as either sets of personal qualities within a culture associated with physiological sex or sets of qualities that evolve in reaction to limitations of existing genders. The evolution of genders functions to meet needs in four domains: (1) psychological: an experience of fit between a core aspect of self and a gender construct; (2) cultural: the creation of an LGBTQþ culture that asserts sets of gender characteristics, which were denied and stigmatized within preexisting cultural norms; (3) interpersonal: the communicating of affiliation and status to enhance safety; and (4) sexual: an erotic embodiment of signifiers of these needs via an aesthetic that structures sexual attraction. I detail how each function affects identity, security, belonging, and personal and social values. Online slides for instructors who want to use this article for teaching are available on PWQ’s website at http://journals. sagepub.com/page/pwq/suppl/index