The American anthropologist Clifford Geertz (1926-2006) has presented a description of religion which has made him one of the most influential key thinkers in the study of religion. His ethnographic work, based on minute research mainly in Morocco and Indonesia, is impressive and testifies to a great stylistic ability. Moreover, his theory about culture and the role played by religion as a cultural system within it, can be considered as being one of the most intriguing and widely discussed conceptual frameworks brought forth up to now. Geertz work is influenced not only by Durkheim and Weber, but also by Wittgenstein, Ryle and Ricoeur. It reflects an empirical-descriptive, hermeneutic-phenomenological approach to the study of religion, focusing on the meaning of symbolic action: on how symbols function as vehicles for meaning. Geertz gives a guideline which can be used in the interpretation of culture and religion. This guideline consists of a concept of culture which is semiotic and textual in character, not a private but a public matter, and not at all an occult entity which is hardly perceptible but a form of social action which can be thickly described. In this introductory text Geertz work on religion will be discussed in the context of the history of the study of religion in general, and in relation to rival approaches in the anthropology of religion such as structuralism and cognitive approaches in particular. After having dealt with his major intellectual roots and ties, we will look at his work on the religion of Java and on Balinese culture, and at his contribution to the study of Islamic culture in Morocco. Next to an analysis of this ethnographic work on religion, we will consider the theoretical and methodological implications of his findings for the comparative study of religion. Finally we will evaluate the criticism on and the influences of Geertz work, and its significance for future research.