This chapter on the relationship between kingship and nobility focuses on the kingdoms of Castile-Leon and Sweden during the thirteenth and fourteenth centuries. It aims to describe research on kingship and nobility in these contexts—ones that seldom take part in the same scholarly dialogues—with a comparative analysis of the varied and shifting political circumstances of medieval European monarchies. In medieval Europe, representatives of monarchy and aristocracy vied for supremacy, often in open conflict. The aristocracy was granted legal exemption from royal taxation while the king secured high-profile military resources for his own ends. The recurrent periods of royal minority in Sweden and Castile were times when the nobility or aristocracy had the opportunity to implement their own political agendas. The chapter demonstrates that both Sweden and Castile share common traits with contemporary kingdoms in western and central Europe, and that a comparative perspective is profitable in order to make connections between seemingly disparate contexts.