My dissertation examines the expansion of Salafi Islam in North and West Africa, particularly the important but understudied ideological and personal ties between reformist Muslims in Algeria, Mali, and Senegal. Beginning in the early 1950s, West African Muslims from what are today Senegal and Mali traveled to Algeria to study at schools run by the Algerian Association of Muslim 'Ulama (AUMA). These men chafed at the power and practices of Sufi leaders, and the education they received in Algeria -- which emphasized the teaching of Arabic, modernization of what Salafi thinkers decried as outmoded forms of Islamic education, and purification of allegedly heretical practices – had a dramatic impact on their trajectories. They returned home in 1953 and established the Union Culturelle Musulmane (UCM), which spread throughout West Africa and became the most important reformist organization in the region. The UCM followed the AUMA's model for educational and spiritual reform as well as its engagement with colonial politics. Like the AUMA, the UCM sought to carve out space for reformist religious authorities and encourage the creation of a new identity, one of an educated African Muslim tied to the Arabophone Muslim world. And on both sides of the Sahara, this project and exchanges between North and West African reformists continued long after independence to shape Islamic identities and politics, social life, and the public sphere. This dissertation researches the doctrinal and political connections between the UCM and the AUMA as well as how the UCM appealed to local Muslims in Senegal and Mali. I then turn to the postcolonial period, to understand how former AUMA and UCM members stayed in contact, the networks that brought West Africans to study in Algerian Islamic institutes, and how these interactions shaped Islamic practice on both sides of the Sahara in a regional context that colonial and later scholarly geographic divisions have obscured.