The name kojic acid was acquired from “Koji”, a fungus or starter inoculum consumed in Japanese oriental food. It is a secondary metabolite organic acid secreted by several species of Aspergillus. Their chemical structure was determined as 5-hydroxy-2-hydroxymethyl-δ-pyrone and produced industrially by Aspergillus species in aerobic fermentation. It has various applications in several fields as antimicrobial, anticancer, tyrosinase inhibitor, insecticide and pesticide organic compounds. It applied in some cosmetic, medicine, food, agriculture and chemical industries. The production of kojic acid is increasing because of its commercial value in various industries. The needing for kojic acid has been constantly increasing. This chapter is to shed light on the history, properties, producer fungi and biosynthetic pathway of this important organic acid. Also, the advance in kojic acid fermentation, medium as well as optimization of nutritional and environmental production conditions are discusses. Some derivatives and diverse applications of kojic acid in industries are described. Future prospects of kojic acid also discussed through this chapter.