What motivated Christine de Pizan's Book of the City of Ladies? This essay argues that the poet's defenses of women were intended to train readers how to envisage the role of Queen Isabeau of Bavaria, who presided over the royal council when her husband, King Charles VI, suffered bouts of madness. Christine's examples of women who ruled in the name of their husbands, sons, and fathers and her references to the ultimate coregent, the Virgin Mary, support female coregency as outlined in Charles VI's ordinances, that is, coregency by a sure guardian of royal authority against the threats posed by the king's male relatives. Although Christine insisted on the female aptitude for power, she never urged that women be allowed to rule in their own names, nor did she appeal for powers that they did not already possess under customary law as representatives of their husbands, sons, or fathers.