Drawing on Barthes's idea of the "shimmer" and Foucault's notion of sex as a mirage, the author shows how sex and gender can appear mirage-like on film, an effect they label shimmering. Analyses include examinations of the fantastic and phantasmagorical shimmerings of sex change in George Méliès's nineteenth-century trick films and Lili Elbe's 1931 autobiographical writings and photomontage in Man into Woman.