This article explores the efforts of French Catholic, Protestant, and Jewish women to morally, spiritually, and physically protect immigrant and migrant women and girls in the late nineteenth and early twentieth centuries. Women of faith worried about the dangers posed by the white slave trade, and they feared the loss of spiritual consciousness among women living far from their families and their places of worship. In response to these concerns, they developed numerous faith-based international organizations aimed at protecting vulnerable working-class immigrants. Upper-class women's work in immigrant aid societies allowed them to take on much greater social and religious leadership roles than they had in the past. Likewise, the intricate, international networks that these women developed contributed to the building of international cooperation throughout Europe.