This chapter provides a comprehensive examination of white oral mucosal lesions, exploring their aetiology, clinical presentation, diagnostic approaches, and management strategies. It begins by elucidating the pathophysiological mechanisms behind mucosal whitening, including hyperkeratosis, epithelial thickening, and surface coatings. The chapter systematically classifies common white lesions (leukoplakia, oral lichen planus, candidiasis, nicotinic stomatitis, and white sponge nevus), highlighting their distinguishing clinical and histopathological features. A robust differential diagnosis framework is presented, emphasizing the integration of clinical examination, adjunctive diagnostic tools (toluidine blue staining, brush biopsy), and histopathological evaluation. Special attention is given to challenges in distinguishing benign/reactive lesions from potentially malignant disorders, with case studies illustrating diagnostic decision-making. The chapter concludes with emerging technologies (molecular diagnostics, AI-assisted pathology) that are transforming diagnostic paradigms. Throughout, clinical relevance is underscored, particularly the importance of early detection of potentially malignant lesions.