The Book of the City of Ladies
Chistine de Pizan was just about a contemporary with Joan of Arc, and wrote The Book of the City of Ladies in 1405, and had them copied and illuminated in an all-female workshop. Pizan tells the stories of powerful women, contemporary, historical, and mythological, and argues for women's moral and intellectual potential in the face of medieval misogyny.
The man or woman in whom resides greater virtue is the higher; neither the loftiness nor the lowliness of a person lies in the body according to the sex, but in the perfection of conduct and virtues.
I chose this quote for how perfectly it sums up the whole book, and feminism in general. Since Pizan would have technically been contemporary with Joan of Arc (she does not, alas, make an appearance in the book), I chose her as the representation of Pizan's ideas.