The marriage of Alfonso VIII of Castile and Leonor Plantagenet was not only the first political alliance between a Spanish kingdom and England in the Middle Ages, but it is also a very interesting case of study for the collaborative and corporate nature of twelfth-century royal rulership in Europe. Queen Leonor was described in the sources as a very capable and virtuous ruler and the study of her reign as consort reveals that she exercised queenship as an active political companion and partner in rule to her husband, thus contributing significantly to one of medieval Spain’s most successful reigns and perhaps setting a model for queens in the late medieval period. Una cum uxore sua, the king did not simply exercise his power and authority in the passive company of Leonor, but with her consort reigned over the kingdom as one body, thus making the most of her family prestige and networks, and fully availing her capacity and virtues for Castile’s political, dynastic and cultural prospects.