Scholars of kingship and queenship have long acknowledged that producing an heir was an expected duty for medieval queens and kings. Indeed, motherhood has been a focal point in medieval queenship scholarship since the field's beginning in the 1980s. Scholars have explored the gendered ideal of queenship and shown that maternity was a key function of the king's wife that enabled medieval queens to exert political influence. Recently, scholars have considered how queens without children were still able to successfully execute their role, by substituting social motherhood and other facets of queenship, like intercession and religious patronage, in place of biological motherhood. Kings needed heirs, but gendered analysis of kingship has been slower to develop than work on other medieval men, or queens, and while fatherhood has received some attention in relation to medieval masculinity, there is less study of the significance of successful fertility for the gendered role of medieval kings. This thesis fills a space that exists between the work on medieval kingship, queenship and the nuanced approaches that are being developed in the new history of infertility. The conventional understanding of 'infertility' as the inability to conceive is limiting, and excludes incidences of secondary infertility, sub-fertility and other uncertainties of reproduction. This thesis investigates the significance and pressure for fertility on kings and queens, by focusing on how royal couples in thirteenth and fourteenth-century England and Scotland, many of whom were not always childless or conventionally infertile, still experienced reproductive difficulties and managed their fertility. The analysis is divided into four chapters, structured around questions about when and why royal childlessness was problematized, and how fertility problems and reproduction were managed by royal couples. The first chapter examines contemporary impressions of the royal couples' fertility and expressions of concern about childlessness. It investigates how royal fertility was written about by chroniclers and uncovers attention to couples' fertility which has been missed by scholarship because many of the couples ultimately did have children. It considers chroniclers' association of reproduction with queens and argues that perceptions of the kings contributed to what chronicles state about royal fertility. The second chapter identifies a pattern of behaviour in the devotional practices of three childless kings, and exposes a connection between the king's behaviours, age and concerns about childlessness. This chapter suggests that royal couples experienced scrutiny of their fertility when the king reached the perfect age associated with masculine maturity in the male life course. The third chapter traces evidence of royal medical care and asks how we might identify reproductive medicine in payments to physicians and connections to medical practitioners and texts. The chapter illustrates key patterns in royal healthcare to illuminate how royal couples medically managed fertility. It argues that royal healthcare was gendered, and reproductive medicine was focused on the queen, but queens had an influential role in the transmission and control of the medical care accessed by the royal couple. The fourth chapter examines the spiritual practices used by royal couples to manage reproduction and remedy fertility problems. It argues that the spiritual practices for reproduction were carefully chosen communications to control perceptions of a couple's fertility, while the spiritual management of fertility was used by couples to communicate broader politically significant messages too. Ultimately, this thesis examines the pressure for fertility experienced by royal couples, and how they navigated this using medical and spiritual support. It moves on from questioning how queens and kings navigated their gendered role in the absence of reproduction and uncovers the significance of fertility for contemporary perceptions of kingship and queenship. It shows how the uncertainties of reproduction affected and were managed by kings and queens, but in different and gendered ways. Ultimately, the thesis demonstrates that a more open analysis of infertility is necessary for understanding with greater precision the experience of childlessness, and the importance of fertility for both gendered roles of kingship and queenship.