While gender has become one of the most prominent subjects in the study of history, including medieval history, over the course of recent generations, the study of masculinity -- of men as men -- has only been explored by relatively few medievalist scholars; Anglo-Saxonist historians in particular have hitherto generally failed to explore masculinity as a field of historical enquiry. This study seeks to fill that gap in the research, and reassess Anglo-Saxon kingship through the lens of gender history and masculinity theory. It focuses in particular on the period of the 'long tenth century', from c. 871-1035. During this time, the Anglo-Saxon realm underwent a number of significant changes: the formation and development of a larger and more centralised Anglo-Saxon state, generations of viking attacks and conquests, a number of serious internal political conflicts, and, perhaps most importantly, the development and promulgation of a religious movement now generally known as the 'Benedictine reform', which greatly influenced not only monastic life but secular life as well. In order to understand the connections between masculinity and kingship in this period, this dissertation first explores what it meant to be a male, and a prince, in the long tenth century. It also asks, 'Who raises royal sons?' -- that is, who was responsible for instilling in them proper masculine (and royal) behaviours? The following chapters then explore the matrix of royal and masculine behaviour into which those sons were enculturated though an in-depth analysis of the range of primary source texts that illuminate tenth-century Anglo-Saxons ideals of kingship and masculinity. Chapter 2 proposes that, while many Continental sources (i.e., specula principum, or 'mirrors for princes') were explicitly written as guides for right kingship, Anglo-Saxon kings and princes had no such guides. They were, this chapter argues, instead instructed through homiletic and political-theological texts that can also be read as evidence of a specific type of 'right kingship' promoted by the monastic authors of the tenth-century Benedictine reform movement. Chapter 3 turns then to another main source of Anglo-Saxon textual material: the literary world of Old English 'heroic' poetry. It proposes that these texts, too, have much to say about how men, especially aristocratic ones, were expected to behave in the long tenth century, the period from which the surveyed poetic manuscripts date. It urges caution in envisioning too strong of a dichotomy between 'heroic' texts on one hand and religious ones discussed in the previous chapter on the other, though, and argues that they must instead be read within the same tenth-century context. Chapter 4 then finally explores the actual performance of masculinity and kingship by later Anglo-Saxon kings and princes, as near as can be assessed in the surviving sources, taking as its model a three-fold conception of aristocratic and masculine 'duties' -- warfare, hunting, and procreation -- and exploring how all three underwent considerable renegotiation in the course of the tenth century. In the end, the dissertation concludes that the myriad changes of the long tenth century resulted in a reimagining of both kingship and masculinity. Moreover, it argues, these new developments in the performance of kingship in the long tenth century strongly intersected with the developments in masculinity in the last centuries of Anglo-Saxon England.