This edited volume examines the rich and often contested discourse surrounding the belief in God’s oneness in Islam. Despite being a foundational tenet of faith, this doctrine has been the subject of intense debate across Islamic history, with scholars disagreeing on its precise nature, implications, and theological boundaries. Bringing together leading experts in theology, philosophy, and religious studies, this volume explores how different Islamic traditions have understood God’s uniqueness. It addresses key debates surrounding divine attributes, God’s relation to creation, and the problem of religious language, alongside the enduring tensions between philosophical reasoning and scriptural interpretations. The book also highlights intra-Muslim disagreements about the meaning of God’s oneness, from disputes between Sunni and Shia scholars to competing perspectives within kalām, legal thought and philosophical theology.