In the sixteenth and seventeenth centuries, aristocratic daughters inherited fiefs in the absence of a male heir. Over the course of the seventeenth century, however, royal decisions and jurisprudence increasingly limited this possibility, imposing masculinity as the primary—though not exclusive—criteria for inheritance. This article explores the legal debates that accompanied this evolution, highlighting a number of changes within the French nobility of this period that reveal a new conception of gender relations. The growing importance of the notion of service, changes to the procedure for proving one’s nobility, and the desire for greater exclusivity within the nobility all reveal how gender was no longer defined in relation to the place and role each individual occupied within the ancestral line or family. Instead, gender assumed an unchanging identity, which, much like nobility itself, was considered inherent to the individual.