The femme fatale as a nineteenth-century motif has been well-researched and a whole body of critical literature attests to her haunting fascination for literary critics. This study interrogates literary definitions of the femme fatale and challenges the notion that the femme fatale is a 'post-Romantic', late nineteenth-century type. Whilst arguing for a more precise discrimination, it considers the earlier emergence of the motif in English Romanticism and focuses on a period where femmes fatales do not appear with marked frequency, but where cultural history emphasises their quality. Tracing such contemporary contextualisations, this study argues for the existence of a multiplicity of different types of fatal women even in Romanticism and for their continuous line of development through to the pervasive motif of the femme fatale in decadent writing.