This essay offers an overview of the history of the relations between science and Eastern Christianity based on Greek-language sources. The civilizations concerned are the Byzantine Empire, the Christian Orthodox communities of the Ottoman Empire, and modern Greece, as a case study of a national state. Beginning with the Greek Church Fathers, the essay investigates the ideas of theologians and scholars on nature. Neoplatonism, the theological debates of Iconoclasm and Hesychasm, the proposed union of the Eastern and Western Churches, and the complex relations with the Hellenic past all had notable impacts on the conception of science held by the Byzantine Orthodox. From the sixteenth through the eighteenth centuries, the Christian Orthodox world did not actively participate in the making of the new science that was developing in modern Europe. It had to deal with the assimilation of scientific ideas produced by Western Christianity, and its main concern was the “legitimacy” of knowledge that did not originate directly from its own spiritual tradition. Finally, with regard to the Greek state, beyond the specific points of contact between the sciences and Orthodox Christianity—pertaining, for example, to materialism, evolution, and the calendar—the essay presents the constant background engagement with religion visible in most public pronouncements of scientists and intellectuals.