Abstract: Growth in Christianity has spurred the appearance of the subfield of world Christianity, whose assumptions increasingly shape scholarship on Christianity. What I term the world-Christian turn, which is often linked to mission studies, yields more comprehensive approaches to the Christian past, connecting local histories of Christian communities to larger-scale historical movements and producing innovative comparative perspectives on Christianity past and present. In Catholic theology, this turn has encouraged new comparative and contextual theologies. Yet support for Christian mission and the world-Christian turn need not go together. Two cases in point: comparative theology tends to eschew mission while the work of Joseph Ratzinger, Pope Benedict XVI, is suspicious of some impulses behind the world-Christian turn and their potential for undermining Christian mission. Such cases notwithstanding, I argue that missiology is a promising resource for the field of world Christianity.