For Mandinga immigrants from the West African nation of Guinea-Bissau living in Lisbon, Portugal, ritual practices are currently provoking transnational debates about African "custom" and global Islam. In Guinea-Bissau, Mandinga conflate ethnic identity with religious identity: to be Mandinga is to "naturally" be Muslim. In Portugal, however, the experience of transnationalism and contact with Muslims from outside of Africa have thrust this long-held notion into debate. In this book, I explore the contours of this debate as Mandinga "argue with ritual" about what it means to be Mandinga and what it means to be a Muslim. Whereas many Mandinga women in Portugal view “traditional” rituals—such as circumcision, "writing-on-the-hand," and healing—to be at once "Mandinga" and "Muslim," others view them as African customs that should be replaced by a more orthodox version of Islam, as practiced in Saudi Arabia. The various case studies in this book reveal an internal debate about Mandinga ethnicity, Islam, and ritual practices, one that is especially expressed along gendered lines. I argue that this internal debate, although intensified by migration, is not itself a consequence of "modernity" but rather has long been central to how Mandinga imagine themselves as Africans and as Muslims in a changing world.