This article uses ethnographic studies of Orthodox Christianities as a way to investigate the concept of 'orthodoxy' as it applies to religious worlds. Orthodoxy, we argue, is to be found neither in opposition to popular religion nor solely in institutional churches, but in a set of encompassing relations among clergy and lay people that amounts to a religious world and a shared tradition. These relations are characterized by correctness and deferral-formal modes of relating to authority that are open-ended and non-definitive and so create room for certain kinds of pluralism, heterodoxy, and dissent within an overarching structure of faith and obedience. Attention to the aesthetics of orthodox practice shows how these relations are conditioned in multi-sensory, often non-linguistic ways. Consideration of the national and territorial aspects of Orthodoxy shows how these religious worlds of faith and deferral are also political worlds. n This article asks what it means to be 'orthodox' from the perspective of an ethnographic view of Orthodox Christianities. We hold that attention to orthodoxy offers a vital perspective on the relationship between religious actors and their institutions that may be missed in accounts of piety or fundamentalism and that sheds light on the continuing influence of liturgical religion and its discourses of truth and authority. A focus on the 'ortho' of orthodoxy-rightness or correctness-gives a clue as to how Orthodox Christianities construct encompassing, authoritative religious worlds in the face of moral imperfection. We investigate how deferral to authority results not in rigid verbal or textual articulations of the true, but in a notion of correctness that is carried in the living and ongoing traditions of the Church, where tradition includes oral, scriptural, aesthetic, liturgical, and other aspects taken together. Correctness thus understood cannot be encompassed by linguistic propositions but leaves open theological and ideological possibilities and modes of engagement with the sacred. We draw on ethnographic studies of (capital-O) Orthodox Christianities-and other institutionally oriented forms of Christianity-to develop Religion and Society: Advances in Research 5 (2014): 25-46 © Berghahn Books