Abstract:Several decades ago, feminists differentiated between the biologically given basis of sex identity (sex) and the socially constructed cultural practices anchored by sex identity (gender). In recent years, many feminists have challenged that distinction, arguing that biological sex is as much a social construct as are the practices comprising gender. I survey two examples from biological studies of sex identity that, by contrast (I maintain), warrant saving the concept of biologically given sex identity. The result is not antithetical to feminism, however, since these studies also suggest that sex identity proliferates beyond the rigid female/male dichotomy. If articulated carefully, this view can avoid metaphysically essentialist baggage while enriching feminist conceptions of sex identity.