While the defence of princely legitimacy had to respond to certain legal and social standards, this technical reality did not act as a fixed template for its eventual performance. This chapter examines the practical and rhetorical aspects of three components of Jeanne’s legitimacy over the course of her whole career: her status as the rightful heiress of Brittany, her exercise of princely rights and responsibilities, and her responses to the disunity of the duchy. Although Jeanne’s claims were rooted in broadly accepted social expectations, not only could her assertions of legitimacy diverge from those of her husband and her predecessors, but she foregrounded different aspects of her status before different audiences; at the same time, other aspects of her official position remained constant even across the major shifts in her political circumstances. Recognizing princely legitimacy as a moving target expands our understanding of what constituted an effective response to a position of weakness, and tempers the ‘ideal’ prince of medieval (and modern) theory with constructions of power more adaptive to the concurrent pressures of princely relationships and authority.