Fever-dreams and nocturnal hallucinations abound in Renée Vivien’s Une Femme m’apparut (1904), one of the first novels to advocate for same-sex desire between women, loosely inspired by her ill-fated relationship with Natalie Clifford Barney, as well as in the latter’s riposte, Je me souviens (1910). As they seek to give lesbian love its own language and make sense of their marginal selfhood, Vivien and Clifford Barney repeatedly tap into the nightmares of the Belle Époque—a liminal, fraught historical period of which they are now seen as emblematic. Vivien, especially, is still portrayed as a ghastly incarnation of the fin-de-siècle lesbian, a tendency which can be traced back to Colette’s portrait of her in Le Pur et l’Impur (1932). Summoning the spectre of the Belle Époque through that of the late Vivien while trying to process her own queerness, Colette offers yet another nightmarish vision of lesbian existence that emanates a dream-like yet oppressive atmosphere. Building on scholarship by Terry Castle and Heather Love, this chapter demonstrates the pervasiveness of nightmares in sapphic narratives of (or on) the Belle Époque and explores the stakes of crafting a queer sense of self from within a culture that considers queerness inherently nightmarish.