Inhibin is one of the most important hormones of the reproductive system, which is secreted by the granulose cells of the ovary and the Sertoli cells of the testes. Inhibin regulates follicle-stimulating hormone secretion involving a negative feedback loop, participates in ovarian folliculogenesis and spermatogenesis, and has great diagnostic potential in assessing the reproductive status and treating reproductive disorders. More than 90 years have passed since the discovery of inhibin, and it is becoming increasingly clear that its action is not limited to the reproductive system, as the hormone subunits and dimers are found in many organs. Further research is needed to study physiological functions of inhibin and diagnostic possibilities of its use in modern medicine. This review examines the structure and various biological functions of inhibin, as well as its role in human reproduction.