This dossier on Siddha system, a collective work of Siddha experts, provides to the readers an overview of the important aspects of Siddha system and its contemporary relevance. The topics cover the origin and development, the fundamental principles, diagnostic methods, holistic health management, special therapeutic approaches, drugs, research and development, education, practice, etc. This dossier will serve as a standard IEC reference material for the general public, inter-disciplinary professionals, stakeholders as well as the upcoming student community of Siddha system.