T. H. White's Arthurian books have been consistently popular with the general public, but have received limited critical attention. It is possible that such critical neglect is caused by the books' failure to conform to the generic norms of the mainstream novel, the dominant form of prose fiction in the twentieth century. This thesis explores the way in which various genres combine in The Once and Future King. Genre theory, as developed by Northrop Frye and Alastair Fowler, is the basis of the study. Neither theory is applied fully, but Frye's and Fowler's ideas about the function of genre as an interpretive tool underpin the study. The genre study proper begins with an examination of the generic repertoire of the mainstream novel. A study of The Qnce and Future King in relation to this form reveals that it exhibits some of its features, notably characterization and narrative, but that it conspicuously lacks the kind of setting typical of the mainstream novel. A similar approach is followed with other subgenres of prose fiction: the historical novel; romance; fantasy; utopia. In each case The Once and Future King is found to exhibit some key features, unique to that form, although without sufficient of its characteristics to be described fully in those terms. The function of the comic and tragic modes within The Qnce änd Future King is also considered. White succeeds in combining the two to create a particular sense of idealism and loss. White combines in his Arthurian books some of the features of an unusually large number of genres. As a result they defy simple categorization but repay close and imaginative study.