This entry explores Martin Buber’s philosophy of dialogue and its implications for psychology, ontology, epistemology, and spirituality. Central to Buber’s thought is the distinction between two modes of relation: I–It, which objectifies others, and I–Thou, which affirms mutual presence and genuine encounter. Buber contends that personal identity and meaning arise not in isolation, but within relational contexts—what he calls the “between.” Drawing from Jewish mysticism, existentialism, and hermeneutics, Buber developed a relational ontology that challenges atomistic conceptions of the self and scientific psychology’s abstraction from lived experience. His work reorients human understanding toward relational knowing, where meaning is cocreated through presence, dialogue, and grace. The “Eternal Thou”—God, for Buber—is encountered in these moments of deep connection. This entry traces Buber’s life, intellectual influences, and major ideas, demonstrating how his dialogical philosophy offers a holistic vision of human existence as essentially relational, ethical, and spiritual.