While at first glance Mérimée might seem rather discreet in the way he uses the Seine in his work, perhaps due to his taste for the exotic backdrop, he gives, by contrast, a strategic role to the river in his only novel, Chronique du règne de Charles IX. A cornerstone in Mérimée’s literary works, this text represents an important step in the endeavors made by the French Romantics to create a new version of the historical novel. This paper examines the way in which Mérimée uses the Seine in his novel. First, the analysis explores Mérimée’s approach to writing a historical novel, and then concentrates on his representation and interpretation of the Seine. In Mérimée’s creative world, the Parisian river becomes a border that must be crossed, an infernal axis which separates distinct universes.