The research in this dissertation was based on the observation that possession and control of land was a key factor in the exercise of royal power in Medieval Ireland between c.650 and c.1200. As scholarship has not yet advanced far enough for an overview of royal power to be written, case studies are employed in this dissertation to explore the exercise of kingship in relation to facets of land use. A broad chronological focus has been adopted in order to accommodate the utilisation of diverse types of sources. This dissertation begins with an introduction to the topic and an outline of the methodology and sources employed in the ensuring analysis. The body of the dissertation is divided into two sections, which are largely defined by chronological and generic factors. In section one (Chapters Two and Three), narrative texts concerning the Eȯganacht dynastic ancestor figure Corc, and saints Éimíne and Senán (Cáin Éimíne Báin and Betha Senáin), which (with the exception of Betha Senáin) date mainly between the seventh and tenth centuries, are examined. Land ownership and rights over land were used in these texts to legitimise kingships, create political alliances and depict royal governance. Cáin Éimíne Báin and Betha Senáin form a generic and chronological bridge between sections one and two. Cáin Éimíne Báin, although the older of the texts, partially resembles the later evidence utilised in section two, while Betha Senáin is closer in date to the later evidence, but is more akin to the earlier narrative texts. In the second section (Chapters Four and Five), the use of grants of land (and rights over land) in royal governance is investigated, by analysing eleventh- and twelfth-century administrative documents, namely the Gaelic notitiae (land notes), in the Book of Kells and Latin charters issues by Irish Kings.