Maria de Luna was one of late medieval Spain's most intriguing female personalities. In a period characterized by powerful male rulers, she combined patronage and a pious cultural program to extend her political power, both formally and informally. However, hers was a figure that did not challenge or undermine the image of the monarch, and instead completed it. Using Maria de Luna, Silleras-Fernandez examines the four pillars of medieval queenship: formal authority, family relations, religious patronage, and household and court through an exhaustive study of her letters and administrative and financial records. This book brings to light the potentials and limits of female power in Iberia on the cusp of modernity and adds to our understanding of queenship in late medieval and early modern Europe.