Can something as simple as friendship have a transformative impact in a divided world? Through a series of richly textured historical portraits and reflections on personal experience, this book shows that boundary-crossing friendships in Christian mission have shaped theologies, built organizations and partnerships, facilitated mission work, and changed attitudes and ways of thinking. This is true in settings as varied as eighteenth-century French women's work, twentieth-century urban Boston, colonial India, the Jim Crow South, and twentieth-century rural Congo. In all these settings and more, friendship has mattered. Boundary-crossing friendships are, however, not easy. Despite their power, such friendships are complicated by race, gender, ability, class, nationality, and other elements of identity, as this book also demonstrates. Friendships are not immune from the divisions in the world, nor a simple cure-all for them. Still, friendship stands as a powerful testimony to the gospel. Therefore, the book calls for more attention to friendship in the study of mission history and more living out of friendship as a practice of mission. In this way, this book pays honor to Dr. Dana L. Robert as a pre-eminent mission scholar and exemplary friend and mentor to others in the fields of missiology and world Christianity.