This dissertation argues that early modern Spanish women engaged theological discourse as apt inquisitors. This project is the first collective analysis of the luteranas, women tried by the Spanish Inquisition as "Lutherans." I examine the manuscript confessions of luteranas tried by the Inquisition of Toledo from 1534-1565 to demonstrate that conflicting discourses of gender and heresy evolve within Inquisition proceedings throughout the sixteenth century. I argue that the earlier luteranas are a critical counterpoint to later mystical writers whose theological activity was often obfuscated by rhetorical constraints that required women to present themselves as ever-ignorant, humble, and submissive. By contrast, The luteranas engaged theology cogently and overtly and often with ecclesiastical and inquisitorial support. Consequently, I bring attention to an often overlooked counter-current in early modern thought by signaling a critical alliance between inquisitorial women and the Inquisition. By tracing how shifting discourses of heresy and gender conflict and comply with Inquisition methods, I signal the Inquisition's dependency upon the same theological sagacity of the female confessants that it condemned.