The thesis explores the problems of genre in fantasy literature. The first chapter locates a set of problems within modern genre theory and relate them to the genre of fantasy. Some of these problems are the problem of definition, which presupposes a stable and static genre, the problem of change, which makes accurate definitions impossible to work with, and the problems of generic systems and hierarchies, which also relate to the problem of change. The second chapter explores these problems in relation to specific theoretical works on fantasy literature, and tries to show how and why most attempts at making a comprehensive theory of the genre fails. Chapter three is a brief study of myth in fantasy literature, meant to exemplify an alternative approach to the genre. In this study I have tried to show that it is indeed possible to treat fantasy as one single genre despite the troubles with fitting it all into one generic definition.