The central task of this essay is an analysis of the relation between apophaticism, trinitarian theology, and divine-human communion through a critical comparison of the trinitarian theologies of the Eastern Orthodox theologians Vladimir Lossky (1903-58) and John Zizioulas (1931- ), arguably two of the most influential Orthodox theologians of the past century. Aristotle Papanikolaou shows how an ontology of divine-human communion is at the center of both Lossky’s and Zizioulas’ theological projects. Papanikolaou maintains that Lossky and Zizoulas hold different views on how to conceptualize God as the Trinity. Their key difference is over the use of apophaticism in theology in general and especially the relation of apophaticism to the doctrine of the Trinity; for Zizioulas, apophaticism has a much more restricted role in theological discourse, and the God experienced in the eucharist is not the God beyond being but the immanent life of the trinitarian God. More specifically, this essay explores a debate between Lossky and Zizioulas, over how to adequately conceive the doctrine of the Trinity as an expression of the realism of divine-human communion, and hence, of the God who is transcendent and immanent. The essay critically analyzes the implications of Zizioulas’s reworking of the patristic category of hypostasis. Zizioulas’s theology is suggesting a paradigm shift in contemporary Eastern Orthodox theology insofar as it prioritizes hypostasis over energies for expressing the realism of divine-human communion. The implications of this study also extend to debates within contemporary trinitarian theologies over the adequacy of the concept of “person” for conceptualizing the Trinity.