Iodine is an essential micronutrient required for the synthesis of thyroid hormones, which regulate metabolism, growth, and neurodevelopment. Iodine deficiency disorders (IDD) remain a significant public health challenge globally, with particular implications for vulnerable populations such as pregnant women, infants, and children. Historically, regions with low soil iodine content have exhibited high rates of goiter and cretinism, emphasizing the public health burden of inadequate iodine nutrition. This chapter provides a comprehensive review of iodine physiology, metabolism, and the epidemiology of iodine deficiency in Iran. It outlines dietary sources and current methods of assessing iodine status, evaluates national public health interventions—particularly the Universal Salt Iodization (USI) program—and presents policy recommendations for sustainable iodine sufficiency to support ongoing public health initiatives.