Allium mardinense Balos, H. Akan & Yıldırım, a new species of Allium sect. Allium, is described from Mardin Province, southeastern Turkey. It resembles A. aybukeae and A. enginii but differs from them by several morphological characters, such as its filament length, inner tepal shape and surface, and anther colour. Diagnostic characters, a comprehensive description, photographs, and a distribution map of A. mardinense are provided.