H. Richard Niebuhr's theological perspective was formed at a time when Protestantism was adjusting to a radically altered position on the American landscape, similar in many ways to the present American Catholic predicament. This essay initiates a dialogue between Niebuhr and Catholic theology at a point that is key to his thought, the theology of revelation. The positions of Niebuhr and Vatican II's Dei Verbum, although developed within different theological frameworks, provide a basis for beneficial discussion. Both view revelation as the self-disclosure of God in Jesus Christ to an historical community that is the bearer of that revelatory experience. For Niebuhr, however, revelation of the God of radical monotheism elicits a faith response to the center of being and value that shatters the boundaries of all closed societies and redirects all moral considerations. His development of the theological implications of historical relativism offers a corrective for the Church's henotheistic tendencies to distort its own meaning and mission by fashioning a closed society. Vatican II took steps to extend the vision of the Church beyond the confining barriers of past ecclesiologies. Niebuhr's theology provides one possible framework within which those first steps can be explored toward a more truly catholic understanding of faith.