The purpose of this study was to find out how religious fundamentalism could be explained by using the theory of Melanie Klein. Through a literature review the answer to the following questions were sought: Who becomes a religious fundamentalist? What precipitates someone to become a religious fundamentalist? Earlier research has focused a lot of its attention on the sociological, political, or theological explanations to fundamentalism, although a growing body of research is emerging regarding the psychological explanations to religious fundamentalism. The results of this study show that there were certain common traits among religious fundamentalists, which can be explained by the ideas of Melanie Klein. The defense mechanism of splitting proved to be prevalent as a trait often seen among fundamentalists. It is also suggested that lower levels of object relations can be connected to religious fundamentalism. However, these findings are contradicted by other research proposing that the level of religious training is a better determinant than object relations development. The Kleinian theory could not answer the questions of this study in total, although, it could present some explanations that need further research.