Through a case study of a Muslim and matrilineal society that is also organized into male age groups, this book sheds light on the question of how matrilineality persists in the contemporary world. On the island of Ngazidja in the Comoros Archipelago, social life unfolds at the crossroads of several powerful traditions. Descent and property pass through women, anchoring families in matrilineal houses. Men organize themselves into age-based political assemblies that govern towns and villages, while Islam provides the legal and ritual framework of everyday life. At the heart of this complex society lies the Great Marriage, a spectacular ceremony of exchange that confers status and reshapes the life course. Both coveted and controversial—admired for its prestige yet criticized for its immense cost—it drives social ambition, economic circulation, and migration, often linking the island to Comorian communities in France. By tracing the intertwined lives of women and men, houses and cities, ritual and migration, this book offers a vivid portrait of Ngazidja and a fresh perspective on the Comoros within the wider Swahili world, where local traditions meet the currents of globalization.