This thesis seeks to relate Christian mystique, which is the foundation of theology itself, and fantastic literature comprising this as a place of both theology and mystical experience. We affirm, therefore, that the fantastic literature constitutes a form of expression of the Christian mystique. What is common in the definitions of these concepts is the dimension of the mystery they both share. For, on the one hand, mystique reminds us of the divine ineffability, in the face of which every expression of language, though necessary to the systematization of faith, is insufficient, since the experience of God goes beyond the limits of rational-logical knowledge reality. On the other hand, fantastic literature introduces into the everyday world the dimension of the unusual, the fantastic, the wonderful that enriches life itself. Both translate experiences that are disturbing and fundamental to human life. These disturbing experiences are intimately linked to the theological and mystical dimension of existence. That is why fantastic literature is able to convey profoundly human experiences, including theological and mystical experiences. From this relationship, the aim is to investigate the personal experience and some fictional works of the Irish writer C. S. Lewis in order to realize how, in his life or in his literary production, Lewis addresses issues related to Christian mystique and theology through the use of fantastic literature.