The terms “Judeo-Christian” and “Abrahamic” are collective religious descriptors that identify points of theological, historical, and ethical commonality between the world’s largest monotheistic religious traditions. “Judeo-Christian” refers to the ground shared by Judaism and Christianity; “Abrahamic” designates elements common to Judaism, Christianity, and Islam. These terms have most often appeared in three contexts. First, scholars of religion have used them for technical, descriptive purposes, to denote the aforementioned religious traditions and the commitments they share. Second, interfaith advocates have employed the terms to identify the particular ecumenical task of cultivating harmonious relations between these three traditions. Finally, in wider public discourses, they have served as descriptors of the religious character of American culture, democracy, and/or national identity. Over time, the terms “Judeo-Christian” and “Abrahamic” have each become important ways of talking about the contributions of the world’s largest monotheistic religions to politics and culture in the United States. However, in American public discourse, “Judeo-Christian” formulations have thus far demonstrated greater reach than “Abrahamic” ones. Between roughly World War II and the mid-1970s, when the United States rose to superpower status and assumed the helm of the Western civilizational project, the idea of America as, in various senses, a Judeo-Christian nation became commonplace. But unlike “Judeo-Christian,” which maps onto a discrete geographical region and a long-standing cultural project, “Abrahamic” tends to be used more narrowly to indicate a set of historically meaningful but geographically diffuse relationships that have become the subject of scholarly and ecumenical concern. Moreover, “Judeo-Christian” emerged in the wake of a massive influx of Jewish and Catholic immigrants between 1880 and 1920 that reshaped the American religious landscape. “Abrahamic” has likewise become more widespread since the immigration reforms of the mid-1960s, which began to bring greater numbers of Muslim immigrants to America’s shores. But the growing embrace of multiculturalism has largely militated against the widespread use of “Abrahamic” as a descriptor of American identity. Proponents and opponents of these terms have vigorously debated their strengths and weaknesses, their uses and abuses. Yet, despite the controversies over their meaning and relevance, “Judeo-Christian” and “Abrahamic” remain important ways of describing aspects of the American landscape in a multireligious age.