Thousands of affluent, white, young Americans travel overseas each year on mission trips organised by Christian churches and organisations. Like secular study-abroad and gap-year programmes, contemporary short-term missions (STMs) are informed by liberal cosmopolitan discourses that elevate affinities to 'humanity' and 'the world' above attachments to nation and locality. Also like secular overseas programmes, STMs aspire to transform young people by immersing them in 'foreign' places. STMs, at the same time, are motivated by a distinctively Christian ethos of 'witness' and self-sacrifice. Drawing on interviews with youth pastors, mission leaders and young missionaries, this article explores the ways that mission leaders encourage young Christians to engage with and to imagine their place in the world. In addition, it considers the particular contradictions presented by Christian variants of cosmopolitan discourse and practice. Missions are intended to be spiritual experiences in which young people recognise the image of God in every person, no matter how abject. Yet young missionaries learn little about the causes of the poverty they observe. By casting the missionised in the role of authentic foreigners and instruments of spiritual awakening, youth missions reproduce the exploitation that have long characterised American evangelicalism's global engagements.