In our religiously and politically polarized landscape, it is worth recalling that the quest for Christian unity is as old as the faith itself. Unsurprisingly, Christian unity has remained a major theme for articles in the journal Church History since its founding in 1932, even to the extent that one of the American Society of Church History’s annual prizes came to be focused on issues of unity and disunity in light of the diversity of global Christianity. The quest to bring fractured Christian movements closer together has taken many forms, ranging from the “top down” of ecumenical councils, church confessions, formal dialogues, and efforts at denominational mergers, to the “bottom up” of grassroots social movements, utopian experiments, missional collaborations, and transcultural spiritual networking. It involves both internal theological formulations that anchor ecclesial identities and external outreach for public purposes such as nation building, ethnic solidarity, or resistance to oppression. Selecting a dozen articles on the subject of Christian unity has therefore required narrowing the scope to one particular angle, namely, to the quest itself. Rather than focusing on the internal theological dimensions of Christian unity, we have selected a range of articles on the striving for unity, better understanding across difference, and the recognition of commonalities between diverse and divided communities. These articles also explore the implications of this aspiration for the public and social dimensions of the faith. The quest for Christian unity is a multi-ecclesial and enduring theme with unexpected implications for the meaning of Christianity in various times and places.