The development of Islamic landscapes in Europe, is first and foremost related to Islamic authority. Religious authority relies on persuasiveness and deals with issues of truth, authenticity, legitimacy, trust, and ethics with reference to religious matters. This study argues that Islamic authority-making among European Muslims is a social and relational practice that is much broader and versatile than theological proficiency and personal status. It can also be conferred to objects, activities, and events. The book explores various ways in which Islamic authority is being constituted among Muslims in Western Europe with a particular focus on the role of 'ordinary' Muslims. This book is available in its entirety in Open Access.