This study examines alchemy's contribution to the conceptual development of sixteenth-century French poetry. It proposes that alchemy, more than a collection of terms, figures, or topoi, functions in this context as a dynamic mode of thought oriented toward spiritual and material transformation. Distinct from Ovidian metamorphosis and from the Christian doctrines of transubstantiation and divine grace, alchemical transmutation reserves effective agency for the human, who brings essential change in things through careful examination and manipulation of natural processes. Through readings from the poetry of Maurice Scève, Pierre de Ronsard, Joachim du Bellay, Philippe Desportes, and Agrippa d'Aubigné, among others, this study demonstrates that the alchemical mode fostered striking insights into the nature of poetic inspiration, creation, and expression, as well as into the relationship of the human with the cosmos and the divine. The introduction traces major contributions to the alchemical mode in the Latin alchemical authors of the thirteenth and fourteenth centuries and includes a reading of the thirteenth-century Roman de la Rose, the first literary work in French to incorporate alchemical thought. The first chapter argues that a commonplace metaphor relating the body of the poet to an alchemical alembic allows for a reconsideration of early modern understandings of poetic production. Originating in the Rose, the metaphor is picked up by Scève and transmitted to his literary successors, who use it to anatomize and examine the process by which poetry arises in and is expressed through the body. The second and third chapters present a sustained reflection on alchemy in Aubigné's 1616 Protestant epic Les Tragiques. The first of these argues that alchemical principles structure the seven books of the poem and allow the author to integrate the horrors of the Wars of Religion into the workings of divine Providence. The second argues that these same principles shape a rhetoric meant to esmouvoir, "move," the reader in the manner of an alchemical transmutation. The conclusion gestures towards the renewed interest in alchemy during the nineteenth century, where poets such as Charles Baudelaire and Arthur Rimbaud use alchemical language to reimagine the nature and functions of poetic language.