Since the 1980s, when it became clear that immigrants from France’s ex-colonies were likely to settle with their families in France, the French have repeatedly questioned the cultural compatibility of Muslim immigrants and their descendants with French Republican values. Recent security concerns about Islamic terrorism in Western countries have reinflamed this debate about French Muslims’ “assimilability,” albeit with a novel focus on the cultural affiliations of French Muslim youth, in particular. The French State and politicians are concerned about survey data showing that, even as such youth have acceded to legal citizenship, they nevertheless exhibit a greater adherence to Islamic norms and more numerous transnational links than their parents’ or grandparents’ generations, and may, for these reasons, pose a threat to French sovereignty. This dissertation investigates these top-down claims of French Muslim youth’s unprecedented religiosity and transnationalism, seeking to ethnographically test the veracity of such hypotheses and to offer a more nuanced, historically emplaced account of youth’s cultural identifications and practices. Based on long-term research with youth ages 13 to 30 who grew up in North, West, and East African Muslim households in Marseille’s northern housing projects, I demonstrate that such youth embody various emic forms of belonging to France, many of which stretch mainstream definitions of what constitutes Frenchness. Through ethnographic observation of these youth while they partook in Arabic classes, spent time with their peers and family, and navigated public space, this work reveals that youth more often perform local cultural belonging than are accorded French cultural citizenship, or the right to be seen and heard as French within the public sphere. I document the forms of alienation from Marseille that youth experience as a result, quite notable among them a gendered reverse migration phenomenon whereby orthodox-identified Muslim young women are planning to leave Marseille for their parents’ home countries and the Gulf States. Two further foci of the dissertation are the role of Arabic language education, both publicly provided and denominational, in shaping youth’s cultural trajectories, and also the analysis of youth’s language practices. I contend that, as diasporic youth draw upon—and play with—standard and non-standard varieties of French and Arabic, they afford the listener unique insight into where they are coming from and where they are headed, or their life-worlds and aspirations.