This article argues that although gender is no longer widely considered to be a property of individuals, the alternative of viewing it in terms of performativity, where it is the outcome of linguistic and social performances, unnecessarily limits the possibilities of thinking of gender as a form of multiplicity that is both internally and externally differentiated. Any attempt to move beyond binary thinking in gender relations initiates a consideration of multiplicity, and the way in which multiplicity is conceptualized exerts a critical influence on the possibilities that are opened up. This article interrogates existing understandings of multiplicity and finds three actual or possible types - multiplicities of the same, characteristic of feminist approaches which we critique through a reconceptualization of desire; multiplicities of the third, characterized by anthropological, transgender and queer theory approaches; and multiplicities of difference and dispersion, typified by the rhizomatics and fluid theorizing of Deleuze and Guattari, Grosz and Olkowski. We propose an ontology of gender as a creative and productive form of desire, realized as proliferation in Deleuze and Guattari's model of the rhizome. Gender identity is accordingly rethought as immanence, intensity and consistency.